You may have heard of the 7 PM rule—it can be your best friend. A "rail day" normally lasts from midnight to midnight. But if you're taking an overnight train that leaves after 7 PM, write the following day's date in the boxes. This way, you don't lose a travel day. Nor do you have to pay for a hotel for that night.

Some, but not all overnight trains have sleeper cars or "couchettes" for a comfier night. There is an additional charge to book a couchette (ask at the ticket counter for more info).

You'll need to know your departure date and the train number (check the "departures" schedule along the left side of the list). The ticket agent will give you a receipt with the date, train number, train car number, and the compartment number where you'll lay your head that night.

Couchettes come in all shapes and sizes. The cheapest sleep six guests in bunk-bed fashion, while slightly more comfy couchettes sleep four. A two-bedded compartment is nice for a couple, while a "single" is downright fabulous. Note that women traveling alone or with a group of women can ask if there are any women-only compartments (or book the whole couchette for yourself).

Another thing about overnight trains: it's not uncommon for them to split in two during the night and head off to different destinations.

On the train platforms, you may notice a colorful poster entitled "composition of principal trains," which lists the main trains that pass through that station and shows the order of their cars (including first and second class, dining car, couchettes, etc.). They should also show which end of the train goes to, say, Berlin, and which goes to Warsaw. If you reserve a couchette, this poster will help you figure out where your carriage will stop when the train arrives. If you skip the reservation, consult this poster to make sure you'll wake up in the city you expect!

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