Tip 10-15% in restaurants and bars. Tip tour guides 5-10 BZ per person, per trip.
Tip hotel folks, room cleaners, etc - ask at the front desk how they distribute tips so that you follow the protocol that will get the money to the folks for whom it is intended. At some resorts there is a built-in service charge in the bill the % varies, and in many cases it is a really minimal amount, so you should still plan on tipping your servers a bit extra.