I'm having a 3 week vacation in Florida in September. I understand that tipping is a bigger issue in the US than here in the UK. Any advice on what is an acceptable percentage for a tip in a restaurant (for good, very good and exceptioanl service)?
The restaurant gods will be pleased with you for having asked. Typical tip in the US is 15 - 20% of the bill, with 15% being pretty much minimum and 20%+ for very good to exceptional service. I try to be fairly generous unless service is awful, though I don't think I've ever tipped more than about 25%. Many restaurants in Miami will now automatically add gratuity to the bill (typically at 18%), but often will still leave a line on the receipt for gratuity (sometimes called "additional gratuity" but sometimes just called, misleadingly, "gratuity") ("gratuity" means the same thing as "tip" if I'm being unclear). Pay attention and review your bill carefully, and if you are unclear, don't be afraid to ask.