Must do's:
Snorkel at Hol Chan/Shark Ray Alley during the day and then go back and snorkel Hol Chan at night.
Get a Belizean Rain Storm at Mango's and then order anything from the menu. Great food, friendly owners. Read the wall in the bathroom. (It's very funny!) Mango's is located by Sunbreeze.
You must go to BC's and get to know Ernie, Mauricio, Charlene & Bruce. Charlene makes the burritos and one of those bad boys with a Belikin is plenty for lunch.
Hear Barefoot Skinny play.
Have stewed chicken with rice & beans. The locals call it "Rice & Beans" from Papi's.
Take a trip to the interior. The Cayo district/Belmopan are incredibly beautiful parts of the country and you'll meet plenty of friendly folk.
Take a day trip to the atolls. Snorkel/dive, whichever you do, just go! Clear waters, beautiful corals. (Glover's Reef is a World Heritage Site, like the Grand Canyon.)
Eat at Capricorn. Not for the food (we thought it was average), but for the atmosphere. Swing in the hammock with your Sweetheart and remember why you fell in love in the first place.
Take a million and ten pictures. You'll never be sorry you did and you'll visit them often. I've got a picture of us at my desk and it helps me hang in there on crummy days at the office.
Our two cents. Have a WONDERFUL trip!
Loie & RobertE