Eurotrip is schlecht.
From the States? Yeah, buy a helluva lotta chocolate, you aren't going to want to eat American stuff once you've tasted Galaxy, Milka, Lindt. I had a Hershey's bar for the first time a couple of years ago, I couldn't believe it. It was disgusting, like budget chocolate or something.
Remember that 'pants' means underpants. Remember that cars drive on the left in London, and anywhere at all in Holland. Oh, and in pubs etc. don't assume there's table service, you might have to order at the bar. But you don't need to tip everyone.
And look out for youths.