I'm in love with Jesus and proud of it!
Do the ONI Sword Base trick to get your campaign commendations up. Almost everyone has done it.
Try to complete as many daily challenges-and the weekly if you can-as possible. On their own the cR payout is small, but they add up.
Don't quit games to increase the likelihood of a high paying cR jackpot.
Play tons of MM (preferably slayer gametypes or SWAT) and FF.
Create custom challenges on Halo Waypoint for big cR payouts... 350 headshots in 3 hours will get you over 12,000 cR, and all you'd have to do is play a bunch of SWAT to get that.
If you have Halo Anniversary, find the terminals and enter the Forunner codes on Halo Waypoint (the Xbox Live App version, not the website). Each terminal pays 7000 cR and the last terminal pays 32,000 cR.
Beat the Campaign on a high difficulty.
[Edited on 03.05.2012 8:29 AM PST]