make a (short -- 3-4 min) screencast. pg et al are probably not going to have time to play with your app to the extent that you'd like (or perhaps at all), plus you get to show your idea/prototype in the best possible light.

if you're feeling lucky, submitting it to news.yc can get some additional attention.

i was a single founder, did this and it helped me 1) bring on a great cofounder and 2) get accepted into yc.