get a friend who also has the game to join an xbox party with you for chat and both of you try to get into a 1v1 deathmatch together
have them create a ton of units and send them to you to kill until you reach point cap, then win. you'll get 33600 points
if you get the flood one, you can both just release the flood and kill them until you both get point cap then have one of you be the loser and blow up all your bases.
you can get 33600 points for the winner and 28800 for the loser if you do this boost method
I know it's basically cheating but, it's the fastest possible way to boost rank in halo wars
if you have one person begin matchmaking until it says 'waiting for players' then have the other person press start to enter matchmaking then, it almost always puts in you a match together.
it also helps to do this at a time of day when the population is really low, late at night you'll see there's like 8-10 players or less in 1v1 deathmatches
and it doesn't really matter what units you use, ie the vultures are worth the most points but, take the longest to make, infantry worth the least points but are fastest to make.
if you can't get into the flood map, you just want the other guy to pump out as many units as fast as possible and feed them to you without losing many of your own units, that way you'll get the max combat efficientcy bonus.
if you do this right, like i said, you'll get 33600 points every win. you could take turns with a friend boosting each other
it also helps to if you let the person winning claim all the bases first, get max pop, build a full army, then destroy all the other bases except their starting one
so the guy sending units to be killed can then claim all the other bases and have all supply pads (need a lot of supplies to constantly send units) and also have max pop so they can queue as many units as possible.