In order to boost experience in Halo Wars for the Xbox 360, you will first need two Xbox Live Gold accounts on two separate Xboxes. Find a friend who is willing to boost with you and have both of you sign into the Halo Wars multiplayer. Make sure you both choose the 1v1 playlist that has the lowest population of players, which is almost always the Tug of War playlist. Because of this, it is highly recommended that both you and you’re boosting buddy have the Halo Wars Strategic Options DLC so that you can access the Tug of War playlist. However, this can still be done in other 1v1 playlists, but it will usually take longer to end up in the same game as your friend. Before you start the matchmaking process, have the player who is gaining the experience play as the Prophet of Regret, and have the other player be Professor Anders. Then have both players find an opponent, and if all goes as planned the two of you should be playing against each other. If not, just quit out or surrender the game and try again (you should almost always be in the same game as your friend if you are playing Tug of War).
Once the game starts, the player who is the Prophet should build the temple and then only warehouses. The Professor Anders player should build one reactor and then only supply pads. Both players should upgrade their bases to the highest level as well as their warehouses/ supply pads. Both players should split the extra bases on the map evenly, with the Covenant player capturing the base with the prophet and the UNSC player using 4-5 warthogs upgraded with chain guns. The extra bases should have only supply pads or warehouses built on them. The Covenant player should also make sure they are upgraded to the third tech level, whether it be from upgrades at the temple or with the forerunner reactors on the map (the elites that can be built from the main can capture these reactors so there is no need to build a hall). The covenant player also needs to make sure that they have fully upgraded the Prophet’s special attack, the cleansing beam (requires the third tech level to upgrade fully).
Once both players have around 20,000 resources, the Covenant player should move the Prophet of Regret to one of the UNSC bases and place the cleansing beam between two of the supply pads. From here on out, the Covenant player is pretty much done doing anything. However, the UNSC player needs to continually build new supply pads over the two spots where the cleansing beam is placed. The supply pads will net the covenant player 10 points when they are destroyed, whether they are completely built or still in construction. Once the Covenant player has reached the 4,000 point maximum that the games have, the UNSC player should self destruct every building they have and make sure all of their units are dead (they can just run them into the cleansing beam).
If everything is done right, the Covenant player will have the 4,000 initial experience points, along with the 8.4 times multiplier, for a total of 33,600 experience for the game, while the UNSC player will have almost nothing. This technique take a couple of tries to get down properly, but once you are used to it you can complete a whole game like this in 25 minutes or less. With this technique you can get the General rank and the Running the Show achievement in only 29 games! But to be fair, you should switch who plays each role for every game so that your boosting friend will also get the experience. Good luck ranking up!