There's one place where I ALWAYS tip - Jimmy John's.
And I can say, all my tipping comes back to me - they make my sandwich correctly, they get to me faster, sometimes they'll slip an extra cookie in the bag... I usually try to tip them two-three dollars each time.
Away back in high school, a load of my friends went to Old Chicago. One of them was... let's say... extremely hyper and "high on life." She was so loud and rude, always calling this poor waiter back and back by name - I ended up tipping him ten dollars extra, cause no one else left a tip. And we had made such a spectacle of ourselves in a nice quiet restaurant.
I only go out to eat with my bestie and we tip 20 percent. When waiters come to a happy table, they're more likely to act pleasantly and come back to check for refills or to bring free bread or whatever. When waiters come to a snarky table, then they snark back. You get what you're giving.
So to sum up, yes, I am pro-tipping. Americans are a lot about showing their money off - waving it around everywhere to all the people who help with small services - like I know many people who get presents for their mailman and garbage man for Christmas.
I've never been to another country, but I think to make sure you're doing the cultural thing, you should ask a local about tipping.