By Rick Steves
Rail passes are pretty straightforward but come with a lot of fine print (worth reading). It's important to understand at least the basics before your first day of train travel.
Validate your pass before your first use. You must activate your rail pass, in person at a European train station, for it to be valid for train travel. Your pass comes printed with an issue date (usually the day you bought it) and must be validated within six months. For example, if May 24 is stamped on your rail pass as the issue date, you must start the pass by November 23. Never write anything on your rail pass before it's been validated.
Validation is easy: At any European train station, present your rail pass and passport to a railway official at a ticket or information window. The ticket agent (not you) writes in your passport number, and the first and last dates of your travel period, and stamps the validation box on the far right. For example, a two-month validity period starting May 15 will end at midnight on July 14. Agents will assume that you intend to use the pass on the same day you are presenting it, so if you're validating it a few days beforehand, write your desired dates (European style, e.g., 15/05/14–14/07/14) on a slip of paper to show the agent. All train trips and non-train "bonuses" (trips on covered or discounted boats and buses) must be started and finished within the valid life of your rail pass. If you have a group pass (i.e., a saverpass), all group members must be present when the rail pass is validated.
You may validate your rail pass before arriving in the (first) country it covers. Let's say you're in Copenhagen with a German rail pass, you're heading to Berlin, and you want the German portion of your route to be covered by your rail pass. At the Copenhagen train station, buy a ticket to the German border and have the agent validate your rail pass at the same time.
Don't get caught with an unvalidated pass: If you forget to do it before boarding, approach the conductor right away to have it validated on board (don't be surprised if you're charged a fee of $5–30).
Fill in travel days (for flexipasses) and trip details. With a continuous rail pass, nobody counts how many days you travel during the validated period. But if you're using a flexipass, you'll have to fill in your travel days as you go. On your flexipass, you'll see a string of blank boxes, one for each travel day available to you. Either just before or after boarding, fill in that day's date in ink in one of the blank boxes on your pass before the conductor reaches you. (Don't fill out the dates any further in advance, in case your plans change.)
Note that a travel day is a calendar day, running from midnight to midnight. You can take as many trips as you like within each travel day that you've marked on your pass. A nice bonus is that a direct overnight train uses up only one flexipass travel day (not two), as long as you board after 7 p.m. and do not change trains before 4 a.m. (you just write the arrival date on your flexipass).
Some passes (continuous or flexi) also require you to fill in your trip destinations on the foldout sheets of your pass cover.
Show your pass if asked. After the train starts, the conductor heads down the aisle, asking for tickets and passes, and checking that they are dated correctly. You may be asked to present your passport, too.
Keep your pass in your money belt. Your rail pass is a valuable slip of paper — if you lose it, it's gone. (Even if you bought the "Rail Protection Plan" when you got your pass, a lost or stolen pass presents a logistical headache.) While some national railways are slowly moving toward paperless ticketing, all rail passes are still only available in old-fashioned hard-copy form. Guard yours carefully.