1. A sig is a signature..It's where we put a picture, our transaction, vouches, and other things..
MMing= Middle man. They basically hold the cash, gold, accounts, they are just the middle man and hold the 2 peoples stuff.
2. Depends if your talking about introducing yourself ( wait idk if there is a fourm specific for that hm ) But the questions this is where them go.
3. To get a good rep you do transactions with people to get their trust.. Sell account, buy accounts, buy gold, sell gold. train, firecape ( if you have did before ), quest , torso, rune defender..Them kinda things.
REMEMBER always use a mm for your transactions make sure that mm is trusted to.
GOodluck any more questions just ask.