I'm starting my fast today too! I agree with Somer on the tapering. I've neglected to taper before my fast began and had to taper during it to avoid the head aches. I'm sure either way is fine. You gotta do what you gotta do.
I'm planning on going 2 weeks this time so let me know how it goes for you. Traditionally, for me, the first 4 days suck and then everything is great.