When and why do you neb a specific post?
What level of standards do you expect other people to neb towards?
Personally, I try to neb as many posts that're funny, make a good attempt at it, are generally kino or tag me/involve me. I've also chosen to neb posts that either make fun of me, ridicule me/my work, and insults, as it technically falls under the last guideline. Even if it's just unpleasant to see, or blatantly disrespectful.
Oh, and I make sure to neb the thread if I'm going to neb any posts. Not doing that is just plain rude.