How do you earn credits in halo reach fast

there are two easy ways to do it. One is to go on matchmaking. There are lotteries now for people who don't quit in the middle of the game, which can give you up to 3,000 credits in one go, so long as you don't quit. The other way takes more time, but it's easier. Go into firefight, select game options, and go to spartan settings. Then go to base traits and then on to health and shields. Change shields to as high as it will go and health to invulnerable. Then, if you have plenty of time, change the time limit to "no time limit" or whatever it is, and change your lives to one. This means that you'll be able to go on forever, but can quit and keep the credits by going out of bounds.