I'm a HP/GW shipper. Believable HP/GW shipper. I've read... one, maybe two stories which I like the 'instant fall-in-love' thing.

The major things that annoy me (and I won't hesitate to review with these), are in this order:

1) Bad Formatting. A big no-no. Space it correctly and grammatically--I won't read badly formatted fanfic. It's terribly difficult to read.
2) Bad Spelling. An occasional typo is fine. Constant bad spelling... ick.
3) Believable characters. Neither Harry, Ron, Hermione nor Ginny are Mary Sues. Please don't write them as such.