Buy souvenirs. But buy useful souvenirs that won’t just take up space or become nuisances.
Showering every day is not a necessity, but smelling good is. Dry shampoo and body spray/perfume are handy.
Long flights are the worst. I already knew that, but it was worth repeating for the effect.
Comfortable walking shoes (sometimes multiple pairs) are a must. You do not want sore feet on your second or third day. Or any day, for that matter.
In some places, beer is cheaper than water. That’s both awesome and terrible, depending on how you look at it (and if you like beer).
Related: Czech Republic is the top beer-consuming country in the world.
Rain coats are essential. Don’t get caught without one. Learned that the hard way.
Jorts are apparently only out of style in the U.S.
Opera is way more popular in Europe than the U.S. I can never understand what they’re singing, but I will always appreciate that kind of talent and dedication.
Hungary is known for its paprika. Poland is known for its amber. Czech Republic is known for its crystal. Austria is known for schnitzel and chocolate and apparently coffee (but I never got to try it and judge for myself). Germany is known for beer.
Travel while you can. It’s exhausting and tiring and will drain you, but it’s worth every second.