1. Find a Daily Challenge that will work. For example, Today's Challenge is "One Spartan Army" (Kill 400 Covenant in Matchmaking Firefight.)
2. Keep playing Firefight or Score Attack (I recommend doing Grunt- Apocalypse until you reach 399/400 Kills. < This will change considering the daily challenge you are working on.
3. Now that you have 399 kills, start up a Firefight or Score Attack game and get your one kill. The Challenge will unlock.
4. Immediately Pull out your Ethernet Cable.
5. Once the Xbox Live box that says "Disconnected from Xbox Live" pops up, then you are good to plug your Ethernet chord back in, and Reconnect to Xbox Live.
6. Repeat these steps as many times as you want until being Credit Locked, and at that point, follow the tutorial below.
*NOTE* This is only todays challenge, and every day there should be a similar challenge which this method will work on.

1. Go to Xbox 360 Dashboard
2. Go to Console Settings>System Settings> Clock> Time Zone
3. Change your time zone to GMT 00 London, if you are from the US. If from the UK, then Change it to Australia

I do Not Take Credit for finding any of these nor do I fully support it. I just figured I would generate an organized tutorial so that this will reduce the spam of all the random threads about these 2 methods. Do not boost constantly. Play the game and enjoy it for what it is.