Forget about multiple boosting partners and/or having friends with ELOs over 1200. I have a solution that will make you virtually unbeatable against anyone on XBL, and it's 100% legal by both XBox and TA standards. That said, it's 100% unethical, and I do not condone this sort of activity. I feel compelled to make the TA community aware of this option as a means of completing the game's achievement requirements but also to be alert to its potential being used against you in casual play... I'm only aware of this strategy as it was successfully used against me earlier today, and there's been some discussion of it recently in the chess universe as a growing epidemic.
You will need a computer (similar to the one you're looking at right now). Do an internet search for free chess engines and download one (there are hundreds and any of them will work just fine for this). Pull up a new game on your computer. Now on the XBox, create or join a ranked game as the black side (you probably could use either side, but it's easier to setup this method and more opponents will join and start a game with you if they get to be white and go first) and any timer EXCEPT HOURGLASS (I'll explain later, I prefer the 5 min Fischer clock when I'm playing). Whenever an opponent joins, he will be on the white side and will go first. Whatever move he makes, enter that on your computer as your move in your game against the chess engine. Whatever move your computer responds with will then be your move on the XBox. However your XBox opponent plays is then your next move against the chess engine. Repeat, repeat, repeat... All you're doing is relaying how the computer would play against your human opponent, and it will win almost all the time. Not even almost; like ALL the time.
Now, the only reason why I caught this guy was that it was taking the same 7-8 seconds/move for my opponent no matter if he was at a critical crossroads or if he had a free piece available that was a no-brainer move. Unbeknownst to him, he was using some very advanced strategies against me but executing them at an extremely suspicious pace. If you think about it, you will have to input your opponents' move, get your move from your chess engine, and then input your XBox move on every turn- there's a certain regularity to the pacing of those same actions regardless of the game's circumstances. So, I'd say you should vary the amount of time it takes you to make your moves so as to not be discovered. Otherwise, you'll have to learn tips as you go.
Hourglass matches will break this method since you won't be able to input the moves fast enough to keep up with the time. However, there's still plenty of players like me who enjoy competitive chess but not at crystal-meth-addict speed, so you should have no problem creating or joining other games than hourglass and beating up on unsuspecting nerds like myself.