I am writing about the sites where you have to make a deposit before buy and the site offers to act as a MM in deals.
How could I know when they are trying to scam me? In general, how do I know if a MM site is trusted?
If you are looking for a MM for a deal here in the forum we have some high trust users that are willing to offer this service at a low cost.
You can either call minerjones or OgNasty.
If you are dealing outside of bitcointalk then you better read more info and suggestions over the internet regarding the site before sending them your money.