Have an itinerary.
Before you go, know where you’re going. Though Europe has dozens of countries that you can visit by train, it’s likely that you have a few countries that you cannot pass up on seeing. If you know that you want to see Portugal, Spain, France, and Italy while you’re in Europe, you will want to focus on buying a rail pass that allows you to step foot in each of these countries. Though you can buy individual tickets for each country, having a set itinerary and finding a rail pass that mocks your itinerary is must more ideal.