Planning for a train trip is pretty straightforward. However there are some things you might consider depending on the type of your trips.
Packaged train trips and railroad vacations:
Many travel organizations provide complete packaged trips or railway vacation packages. Usually there is almost everything included: train tickets and reservation, accommodation, meals in the restaurant car, sleeping car reservation if appropriate etc. You just have to organize your travel to the starting point and your return travel from the end point. Some of these packages offer guided tours as well so you have a program for you organized during the various stops of the train. Prices vary greatly depending if you use a train trip package based on a standard train or a special train specifically designed towards railway voyages which tend to use special luxurious or antique vintage cars etc.
Do it yourself / individual train trips:
If you prefer to manage your train vacation by yourself you will have to plan more in more detail and do some research. But planning and researching might be a fun and exciting phase as well: The great advantage of self organized train trips is that you can select your route / routes as you wish. Today the web offers every tools which might be necessary to narrow down your possibilities. Are you interested in cities and their history? Or are you more into nature? Mountains or deserts? Rivers or beaches? Using online maps (like google maps for instance) give you a good background information about the geographic nature of your envisaged train trips. After deciding the continent / countries you might traveling to you just have to research train connections. This is easily done by going over to the websites of the railway operators. Virtually all of the railway operators do have online tools concerning their train connections. You can even buy your tickets and order your reservations with these tools. If you are going during seasonal peak time (for most regions the summer months) you will have to book your hotel accommodation in advance. There is a huge bulk of specific travel literature for most of the famous trains and railways.
Multi-day train trips / railway voyages:
Obviously if you are spending multiple days in a train or if you hop from city to city by train you would need to carry your equipment with you during the train travel. Carrying luggage into a train is not as bad as you might think. Just make sure that you are a bit organized and take care while selecting the type of the bags. Don’t use too big suitcases. A rucksack comes in handy while searching for your reserved place in the train. Too many pieces of luggage may be a little bit annoying to carry when changing trains etc. So try to be a little bit selective when choosing your travel items. Some trains (like for example Australia’s famous Ghan) even set limits to checked-in as well as to on-board luggage (in size and in weight). Some luxury trains require certain clothing standards so you would need to bring some formal clothes. In general you should take with you some clothing for cold evenings/nights even during summer and in regions with warm temperatures. The cooling of the train compartments is sometimes pretty intense. A good reading book for long evenings/nights is also highly recommended.
Single-day train trips:
Obviously single day trips from a base (e.g. a city) are really easy and there is nothing special to organize about it. Just research the various connections and time schedules and book your reservation and buy your ticket which is quite easy these days using online reservation systems. Most train operators do have online reservation systems in various languages so you should not encounter any problems.