Anything in particular I should know before I get there
The coffee is English and expensive! Seriously, the American Hall is well worth a visit. It's too small (aren't they always) and dominated by the B52, but a good selection of aeroplanes (sorry, airplanes). On the walk up to it there is a wall with silhouettes of American aircraft lost in Europe during WWII. The sheer numbers are staggering, and thought-provoking. Others you might find interesting are the RAF Museums in Hendon (London) and at Cosford in Shropshire.