When it comes to metagaming and bending/breaking the rules of the server, I understand the DM's are serious.

But when I see new players (by new I mean folks who's names I don't recognize and aren't among the 'veterans' of this server) metagaming or abusing mechanics (corner sneak, etc), I make mention to them that that action/behavoir/tactic is frowned upon.

But at what point should I turn and make a DM report? I don't want to bust out some newbie and make him think the community is a bunch of snitches. THough I do know that there must be some point at which I must make a comment to the staff.

Some guidelines on this would be clear since I tend to play mainly during 'slower' times (mid to late morning).

Link them to a page on the forums or website that notes the rules you believe them to be in violation of, then leave them alone. If you see them continually doing it despite having shown them the rules as written by the DMs, make a report.