In reply to TheDrunkenBakers:
For a half marathon, I wouldn't usually do anything particularly special this far out, and unless you do something truly stupid, it's unlikely that you'll do much to change your finishing time one way or another.
Looking back at my last half marathon, at Alloa this year, I did a 6 mile trail race the weekend before, an easy 7 miles on the Tuesday, an easy 5-mile club run on the Wednesday, an easy 6 miles on the Thursday, and then nothing on Friday or Saturday. No special preparations with diet, although I tend not to drink much alcohol the night before.
Don't make any significant changes to what you've done before. If you've been doing the distance, simply try to replicate the things that have worked well in the past.