1.Sign up to XBOX Live Rewardshttp://rewards.xbox.com/
2.Then check out the Gamer IQ Quiz:http://rewards.xbox.com/gamer-iq/
Scroll down and see offers available including:
1.Buy It, Play It,
Get 400 Microsoft Points
Purchase Halo: Reach - Defiant Map Pack or Halo: Reach Games on Demand from April 1st to May 15th, 2011 and get 400 Microsoft Points.
The map pack is 800MSP but with 400 points back effectively 50% off.
2.Get the Halo Reach
Banshee for Your Avatar.
From now through May 15, spend 200 or more Microsoft Points in the Xbox LIVE Marketplace and get a Halo Banshee avatar item free!