The main thing is to try and hit the right pace. You will probably have a finishing time in your mind, well, you will probably run about 2-5% faster than that, if you get the pace right. Mainly, don't get carried away with the rush at the start.

Having no idea of your standard, let's work on the assumption you will run 2 hours (you can scale it up or down accordingly). You will therefore actually run about about 1:55, that's 8:46 mile pace. So, start at that pace and stick with it until about nine or ten miles. Don't be tempted to chase after the big fat person who has just passed you at 3 miles! IF (!) you have anything left at 9 or 10, now try pushing on a little bit faster, only a little bit, you won't be sprinting.

I've done dozens of half marathons, and my best (76:40)came when I started at even pace and pushed hard over the last 3 or 4 miles.

No matter what you do, you're going to hurt! But but it's well worth it.