Uphill static starts from sign posts cause me grief. Most of the instructional tips that I read say to make sure that the crank is at about the 2 o'clock position so that you can give a strong powerstroke, and of course lean forward. Recently I've increased my success by focusing on the second stroke.
I've noticed a tendency to stall even if I lean forward, start the first stroke at 2 o'clock and hit the gas. I fly off the front and leave the uni behind. Sometimes I feel like I've hit a stick, but when I check around, there isn't even leaf that I can blame it on. The mental image that has been working for me is to make sure I carry the power to the second stroke so that my wheel momentum builds and I can make some progress up the hill. Focusing on that second stroke gets me moving.