what to look for whe buying used heads?

I'm going tonight to check out a set of used TFS Twisted Wedge Heads and need to know a few things to look for that would indicate heave abuse, wear, or anything else that would mess up the heads. Also when checking out a used cam you just need to look for any nicks and/or scratches on it right?

Is there any areas that cause more problems than others that I really need to look into? Please let me know everything that I need to be looking for.