Long time leecher (well I never found anything to post that haden't been posted before)
I did some searching and it might fall under "common sense" or "clever use of game mechanics)"
Well if you are a tank or healer with short ques and are tired of failed pugs or just tired of doing heroics (like me) but still need more faction rep you can go about getting it this way.
LFG for SFK HC specific, this instance has easy, fast and somewhat plenty trash before first boss. Clear trash (about 300-400 rep, depending on class and guildlevel) and just as the last trash died, leave group. (1-20 sec after it died). Somehow this dosen't give you the deserter debuff (not in any of my 10+ tries atleast) or the "use the LFG tool too soon". So you can just re-que in a min (to ensure you dont get back into the group you just left).
I don't know why, it might be as I said already known, atleast its diffrent from the "leave before rolling on loot" as I have never found that to work.