So i'm using the nWoD rules for a zombie setting game and we're just starting out.  what is a good system for handing out experience.  I was considering 1 exp for every 10 constructive posts.

Any tips would be much appreciated.

Actually, as far as concrete systems go, that sounds pretty good. I'd caution against such regular doling out of experience, but since play-by-post is slow in general, it might work to establish a steady rate of advancement. It's either that, or inform the players that they bloody well better make characters they like, because they'll be stuck like that for a while.