'I have seldom heard a train go by and not wished I was on it,' wrote Paul Theroux at the start of The Great Railway Bazaar, his account of a train journey from London to Tokyo. Commuters on the London Underground or the New York Subway might not share this sentiment, but for those of us with a more relaxed attitude to time, there's nothing quite like the anticipation of boarding a train, settling into a window seat, and letting the pleasure of travel take over. For trains are more than just a means of getting from A to B.

At one extreme, they give the traveller an insight into the everyday life of the countries they serve. To see and experience India away from the main tourist attractions, there is no better way than to take the train. Railway stations themselves are a microcosm of Indian life. The homeless and beggars may spend their whole time cooking, drinking, washing, and sleeping on platforms. Then there are the tradesmen - chai wallahs, booksellers, stallholders - and, of course, the crowds.

At the other end of the spectrum, South Africa's Blue Train from Cape Town to Johannesburg has gold-tinted windows, haute cuisine and en-suite accommodation, and is generally reckoned to be the world's most luxurious train.

You can take a train for a one-off trip, or you can spend your whole holiday on one. Sometimes there is no alternative form of transport - unless you are a mountain climber, the only way of ascending the Jungfrau in Switzerland is by rail.

Planning the journey

Wherever you want to go, planning is essential. In some parts of the world, trains run much less frequently than in the UK. There's a line in Patagonia whose regular train plies only once a week. Miss it and you have to wait seven days for the next.

The most comprehensive guides are Thomas Cook's European Timetable and Overseas Timetable. Both include shipping services as well as railways; both concentrate on major routes. For minor lines, one must consult local timetables. The best known is Newman's Indian Bradshaw, which contains every passenger train on the 35,000 miles of India's rail network. Sometimes there is no way of getting advance information. In parts of South America, the timetable consists of nothing more sophisticated than a handwritten poster or a blackboard at the local station.

Tickets

1. No railway administration likes ticketless travellers. You might just get away without paying in places such as India, especially if you enjoy riding on the carriage roof, but in many countries fines are stiff for passengers without valid tickets. The same goes for riding first class with a second-class ticket.

2. Train travel can be incredibly cheap, particularly in developing countries. If you want relative comfort and space, use first-class accommodation (if it's available) - you won't have to raise a mortgage.

3. There is now a proliferation of discounted tickets. Age, time and day of the week, advance purchase, duration of journey - all may have a bearing on the price you pay. Rover tickets offering unlimited travel within a country or geographical area are real value for money. Finding out about the best buys is, however, not always easy. High-street travel agents are not the best informed when it comes to rail travel. Try to find one who specialises in railways, such as Ffestiniog Travel. As a general rule, it pays to book as much of your overseas journey as you are able to in the UK before you set out. This will save you money, as well as possible hassle later on. A lot of patience is sometimes required if you try to book locally. The sale of tickets is not always the relatively speedy process it is in the UK.

Luggage

Travel light. It's amazing, when looking at pictures of Victorian travellers, to see the massive trunks they took with them. What did they pack?

The station porter may be a rare species in Britain but flourishes elsewhere - at a price. Even so, a mass of luggage is an encumbrance on a train. Pack essentials only. Choose according to the length of the journey and the climate of the country.

A word about security. Petty theft is a fact of life almost everywhere. Unattended luggage is easy game. Remember that in many developing countries the value of a camera may equate to several months' average wage. Keep money and other valuables on you. If you have to leave baggage, make sure it is locked and try to chain it to some immovable object such as the luggage rack. Above all, make sure you have adequate insurance.

Food

On long train journeys, find out in advance if food and drink are likely to be available. On-board catering should be indicated in the timetable, though standards and prices vary enormously. South African dining cars offer superb food and wine at modest prices. France is disappointing - food on the high-speed TGV is no better than average aircraft-style meals. Catering on the Trans-Siberian Express is, by most people's accounts, hardly bearable.

Don't overlook the possibilities of station restaurants, though Western stomachs should be wary of platform vendors, especially in Asia. Their wares look colourful but can have devastating effects. Similarly, treat local drinks with caution. Peru has its own version of Coke - green Inca Cola - as nauseating to look at as to drink. Chai (sweet, milky tea) is the safest drink at an Indian railway station and the cry of the chai wallah is a distinctive feature of train journeys.

Health

The first item in my personal medical kit is a bottle of eye drops - essential for countries where trains are still pulled by steam engines. Sooner, rather than later, the inevitable smuts will be acquired.

Other than this, there are no special health hazards associated with trains, assuming you won't be riding on the roof or hanging onto the sides. But a long journey is not the best way to pass the time if you are unlucky enough to be ill, and on-board 'bathroom' facilities are pretty primitive in many places. So it's important to take the health precautions necessary for the country you are visiting.

Sleeping

There's no experience quite like sleeping on a train. Again, if you intend to do this, plan ahead. Find out from the timetable whether sleeping facilities are available, and if so, what they are. There may be a sleeping compartment with fresh sheets, its own loo, and an attendant. Couchettes are popular in some countries - beware, the sexes are not always segregated.

In India and Pakistan, sleeping accommodation means a bed-roll spread out on an ordinary compartment seat, if you're lucky; and it's worth remembering that the more important stations on the subcontinent have retiring rooms where a bed can be rented for the night.

Whatever the facilities, a supplementary fee and advance reservation are almost always essential, though greasing the palm of the conductor often works wonders in places where such dealings are a way of life.

How to travel

First or second class? Express or slow train? By day or by night? The answers depend on the money and time at your disposal, and on the aims of your journey. Do you want to be cosseted from the outside world and pampered with luxury? Do you prefer to mix with local people? It's entirely up to you. The choice is enormous. Remember one golden rule: the more comfort you want, the more you will have to pay; and the greater will be the likelihood of having to make reservations in advance. Conversely, second-class travel is cheaper, usually does not need to be booked ahead, but will inevitably be more crowded.

Incidentally, some countries have more than two classes. India has a plethora, though you won't necessarily find them all on the same train.

Suggested routes

Starting at the top of the market, the Blue Train has already been mentioned. In the same league is the Orient Express. Can there be a more romantic way to arrive in Venice than by this train of restored elegant carriages? So successful has this up-market concept been that sister trains now operate in Malaysia/Thailand and in Australia. Other trains designed specifically for the tourist trade include India's Palace on Wheels and Spain's Andalucian Express. Though the daily train that took passengers from Montreal to Vancouver and vice versa ceased running a few years ago, it is still possible for tourists to cross the Rockies by luxury train.

Canada aside, the long-distance train does survive in everyday use in many parts of the world. The Trans-Siberian (or Rossiya to use its local name) runs daily from Moscow eastwards to the Pacific coast. One can still cross the USA by rail, though not as one continuous journey. Trains travel vast distances in India, and in China where a new 'first-class' train links Beijing and Hong Kong. The Indian Pacific traverses the complete width of Australia from Sydney to Perth, whilst the Trans- Alpine crosses the mountains of New Zealand's South Island.

There are not many railway-less countries, and the possibilities for train travel are limitless. Don't just stick to the well-known routes. Branch out and see what you discover. The most memorable journey is often the least expected. Tucked away in a remote mountainous part of Peru are the towns of Huancayo and Huancavelica. The train takes all day to go from one to the other, stops everywhere and is full of people going to market with their produce and livestock. There are tunnels, steep gradients and river gorges and, all the while, the Andes form a stunning backdrop. A humble line; an extraordinary and exhilarating experience.

Better known and in almost equally breathtaking scenery is the narrow-gauge railway linking the hill station of Darjeeling to the plains 1,800 m below. In just over 80 km, the diminutive engines of the Darjeeling Himalayan Railway climb by way of zigzags and spiral loops into the foothills with stunning views - on a clear day - of Kangchenjunga, at 8,500 m the world's third-highest mountain. Parts of the track are often washed away in the annual monsoons, and it's a wonder the line has survived, especially as the journey by road can be done in half the time it takes by rail. But if the trains are running, it's a journey not to be missed. Such is the unique character of the line that it has just been declared a World Heritage Site by UNESCO.

Special interests

To many, railways are a hobby; some would say an addiction. Every aspect of railway history and operation has been studied in great detail, but it is the steam locomotive that commands the most devotion. Steam has an atmosphere all of its own. One can see it, hear it, smell it, feel it and taste it. Steam buffs travel the world to experience its thrill.

China is the enthusiast's Mecca. With cheap labour and plentiful coal supplies, China was still building steam engines in the late 1980s, and there are hundreds at work on the country's railways. In contrast is Cuba, where ancient engines are brought out of retirement for the annual zafra (sugar harvest) to pull cane from the fields to the mills. In this steam paradise, it's possible to combine a beach holiday with the joys of watching trains.

Elsewhere, the number of countries where steam is in everyday use is dwindling. Poland and the eastern part of Germany are the only European ones. Further afield, steam lingers - just - in Zimbabwe, Indonesia, Burma and Argentina. Sadly India, long regarded as a bastion of steam, has finished with steam on all but a couple of branch lines. There is a compensating increase in museum and preserved railways, but to the purist these are a poor substitute for the real thing.

Specialist travel operators for the serious enthusiast include Steam & Safaris, Travel Bureau Railtours, and Dorridge Travel Service. Many tours include general-interest elements to cater for non-railway partners.

Weighed down with cameras and all the accoutrements of photography, steam buffs are instantly distinguished from their fellow travellers. Do not despise them! Their motives for the journey may not be the same as yours, but they're the experts to turn to when the unexpected occurs.

Remember that trains run late the world over - sometimes very late. Occasionally they are cancelled. Connections are missed. Landslides block the line. In these circumstances, your timetable may not be much help. It's a fair bet the enthusiasts will know the solution to the problem - you hope.

Reading material

Trains are places for meeting people. You will rarely be on your own. It's only in England that strangers never converse. Nevertheless, make sure you put a good book in your luggage. Every journey has a dull moment.

Books about railways are legion. Thomas Cook has a series of handbooks for 'rail touring'; and Bradt has books on rail travel in specific countries such as India and Russia. Paul Theroux's The Great Railway Bazaar remains the most readable account of one person's journey. Start and you won't be able to put it down.

To appreciate the atmosphere generated by the steam locomotive, browse the transport section of any large bookshop. For a sample, your contributor immodestly suggests his own books Steam Railways Around the World and Steam Through Five Continents.

Above all, buy a timetable. It is a mine of information. My Pakistan Railways timetable tells me the cost of a bed in the retiring room at Karachi. Breakfast consists of 'choice of two eggs, two toasts with butter and jam, pot of tea'. If I want to take a rickshaw with me as part of my luggage, it will be deemed to weigh 150 kg and charged accordingly. On another page comes the solemn warning: 'Passengers are requested in their own interest not to light or allow any other passenger to light any oil stove or any other type of fire in the passenger carriages as this practice is not only fraught with dangerous consequences but is a penal offence under the Railways Act.' Fascinating! This timetable could keep me occupied for hours.

Finally, turn the pages of the timetable and look at the names of the trains. Whose imagination fails to be stirred by the Frontier Mail, Himalayan Queen or Shalimar Express?

Trains are not some sort of time capsule. They seem natural - almost a part of the landscape. They certainly reflect the characteristics and atmosphere of the countries and communities through which they run in a way air travel, cruise ships or air-conditioned road coaches can never do. Flanders and Swann put it rather differently in one of their songs: 'If God had meant us to fly, He would never have given us railways.'