The direct, one-on-one approach seems to be key above all else. If you say "I need you to buy my book!" to a room full of 100 people, they’ll each think to themselves "Eh. Probably everyone else will. I can sit this one out." If you say "I need you to buy my book!" standing nose to nose with someone, they’re going to have a much greater difficulty deflecting it.
I’ve gathered the vast majority of my readers from facebook. When I posted "Hey, I need you to buy my book!" statuses, I’d get about three new buys. When I started directly sending personal messages to literally everyone on my friends list, I started raking in as many as 20 supporters a day.
That seems to be "a" important thing to remember when driving buyers. I’ve officially messaged everyone I personally know at least twice now, and I’ve pulled in about a quarter of them as supporters so far. I’m starting to stall out too, though. I’ve earned about 20 referrals from friends as well, but there comes a point where you’ve mined your personal contacts for about all you’re going to get.
Definitely talk to people who have successfully been funded and take their advice seriously, even if it goes out of your comfort zone. I wouldn’t have gotten this far without that.
Beyond that, I can’t really say what it takes. I’m hoping a snowball effect will hit Tantalus Depths (shameless plug) from the inkshares community when it gets closer to Quill goal. Even though I don’t plan to stop at Quill, I’ll be able to use it as a measurable goal to promote a sense of urgency, much like I was able to do with the Geek and Sundry competition. Telling people your book is in a contest that ends in three days is more likely to pull in their support than telling them you’re trying to get 500 pre-orders in the next 2 months. You kind of have to take it in little chunks.