Speaking as a former queen of anal (I gave my crown to my gay cousin when he left to teach english for a year in Thailand), I recommend lots of booze beforehand, an open mind, and regular breathing. Don't bother with lube because it only makes it trickier and prolongs the awkward figuring-out-the-right-angle moment. Also have lots of regular sex first, I theorize that it loosens up the muscles and puts you in The Zone.

I'll ask my husband if he has anything to add.