This is a good topic. I always tip at restaurants like I do at home, and make sure I take care of any hotel staff that has provided any service for us. I also tip taxi drivers a couple bucks at each drop-off. I've heard drivers complain that some tourists negotiate a price and then don't tip on top of that.
However, I am still a little confused about places that charge a "Service Charge" (i.e. Ivan's). I have heard that the Service Charge is a tip and that you are welcome add to it if the service is good. I've also read on some websites that the Service Charge is not considered a tip, and you are expected to tip a full 15-20% on top of that. What's the right answer?