By Rick Steves
It's wise to carefully compare passes to find the best fit for your itinerary and style of travel. The range of options may seem intimidating, but mostly it's a matter of simply knowing which countries you intend to travel in and for how many days.
First find the pass that best matches the area you'll be traveling in. If you're planning on covering a lot of ground by train, you probably want a multi-country pass, as it generally makes little sense to cobble together several single-country passes.
A Global Pass, covering the widest area, gives you most of Europe by the tail, buying you unlimited travel on all public railways in most of Europe (Britain is the big exception). If you've got a whirlwind trip planned, the Global Pass is probably the best way to go. (You need to essentially travel from Amsterdam to Rome to Madrid and back to Amsterdam to justify the purchase of a one-month Global Pass.)
For a less ambitious multi-country trip, consider a Select Pass, two, three, or four adjoining countries (though a few pairs of neighboring countries aren't available as two-country passes). If you're traveling just a tad beyond four main countries, consider whether buying one or two extra point-to-point tickets might be cheaper than bumping up to a Global Pass. If a certain multi-country regional pass, such as for Scandinavia, happens to fit your plans, it can be even cheaper than a Select Pass.
Virtually every European country has its own single-country pass. These are especially worth considering for Britain (which does not participate in the Global Pass or Select Pass) and for Switzerland (where its pass covers more than just trains). The relative value of a single-country pass over individual tickets really varies across Europe, so it pays to price it out before buying one.
If you plan to linger for a few days at most of your destinations, a flexipass makes the most sense, as it lets you pay only for the days on which you actually travel. Most rail passes are this type. You don't have to decide beforehand which days you'll travel on, but you do have a certain window in which you must use up your train days (usually two months after you start using the pass). You can take as many trips as you like within each travel day, which runs from midnight to midnight (though most direct overnight rides can count as only one travel day on a flexipass — thanks to the "7 p.m. rule" an overnight train uses up only one travel day, as long as you board after 7 p.m. and do not change trains before 4 a.m.).
A few passes are also available as a continuous pass, which can save you money if you plan to travel nearly daily and cover a lot of ground. Global, BritRail, French, German, and Swiss passes offer this option. If you have a 15-day continuous pass, you can ride the trains as many times as you like for 15 days. The number of days you can travel with a one-month continuous pass depends on the month you start traveling: If you set off on any day in February, the pass is only good for the next 28 days; if you start in July, it's good for 31 days).
For those with open-ended plans, continuous passes can provide an extra sense of flexibility. Let's say you're planning a three-week trip and choosing between two versions of a Global Pass: a 22-day continuous pass and a cheaper 10-days-in-two-months flexipass. For not much more money, the continuous pass gives you the freedom to take any train without wondering if a particular trip justifies the use of a travel day.