Odd question. What happened when you asked for it?
You scribble on your left palm with the imaginary pencil in your right one. International symbol for I am ready for the bill.
Yup, do as Alan suggested. Also, you can simply politely ask the waiter/waitress; it's not considered rude to do so like in the US. In France, say "La note, s'il vous plait."
I third what Alan says. That's been my experience in foreign countries as well. As a sidenote, after spending 8 months living in Europe, this was one thing I sort of missed - the relaxed dining culture. Sure, by American standards service is usually slow, but on the flip side, nothing ever seemed rushed, which I always found very relaxing.
I really enjoyed the relaxed pace at bars and restaurants in Europe this summer. Once you're seated it's your place for as long as you want it.
NOTE: Blogspot has been eating some comments, and there doesn't seem to be anything I can do about it. IF your comment doesn't appear, it's not you, it's not me, it's the genuiuses at Google. Sorry--