What's the general rule for bumping topics? I've been verbally warned for this and I don't really want that happening again.

If you have an update for something its okay. It's also usually good with the mods if you do it in a request topic or similar after waiting a week or longer and getting no replies.

General rules for bumping topics:
-They have to be your own topic.
-Only do it if it has been more than 3 days.
-Unless you have an update the second point doesn't matter.
-When bumping a topic don't just write. "Bump." Or "Comments please."
-Like the last one make sure it's a meaningful bump posting about updates to said thread.

Hope that helps. =)

Quite helpful actually, thank you.