I don't know your running background. (There's a pretty active half-marathon group on the Newbie board.) To me, the big difference from 10Ks and shorter races is that you have the chance to flow into the race. I try to go out hard but relaxed and try to feel comfortable. It's a race in which you can let the training take care of you, i.e., you have it or you don't. In recent years, I've been running decent negative splits, so I may be going out too slowly. Once you hit mile 9, you should be confident that you'll finish so you can try to pick it up a bit. Particularly for the first one, there's doubt about whether you can make it, but if you feel good when you hit 9 (or maybe 10) you'll have confidence to make it the rest of the way.

Good luck, and have fun.