i'd also say spend a lot of time coming up with a story and framing your opportunity in the biggest possible way. this was something i really underestimated -- initially we'd just show a list of features and expect everyone to arrive at the vision we had in our heads, but really it's the other way around -- the features drive a more important story and vision.
a story is also a lot easier for an investor to retell and get other people excited about than a laundry list of "um, it does this, and this, and this..." remember, VCs have to then turn around and sell their own general partnership on the idea, so give them the ammo they need to do this effectively.
also -- practice your pitch until it becomes mechanical. not so much by standing in front of a mirror (though that helps too) but rather by debugging it with individual angels or mentors, so that by the time you pitch the investors you really want you've already seen most of the universe of possible objections and surprises and can handle them effectively.