If you're coming across the pond, get your Visa all taken care of as early as you can.
A few notes about us colonials: If you drink beer from a major American brewery, you'll think you are drinking water. It isn't like a real brew at all. Micro brews are what you'll need to drink to have something that even remotely resembles a real beer. Secondly, the beer is served a few degrees above freezing, so you won't need ice chips. Third, it isn't a real pint, it's only 16 ounces.
Other things: to us, a jumper is a woman's dress, we wear "sweaters," shopping trolleys are called shopping carts, if you smoke, don't ask for a fag...speaking of smoking, Americans don't have the habit of offering a cigarette to others when they open a pack. They aren't being rude, just not the custom. We pronounce a lot of the Queen's words incorrectly, and as evident by my writing, we take major liberties with the written word as well.
As a whole, though, we're a fun lot. Have fun!