In Madden NFL 12 for the PS3 and Xbox 360, you earn coins in the Madden Ultimate Team mode (aka MUT) in several different ways. Playing games and performing well gets you coins, but you would have to play a ton of games to be able to purchase anything nice. So how do you easily get hundreds of thousands, or millions of coins without playing a thousand matches?
First, play a few matches in MUT to save up several thousand coins. Start buying the bronze packs, open them, and sell the jerseys, stadiums, and coaches for the minimum amount possible which is 1000 coins for bronze cards. The bronze pack costs 1000 coins, so just by selling one card in the pack you make your money back. Make your duration short as well, since auctions are sorted by duration, so yours should appear near the top.
The reason this can work well is because of the collections. You earn coins and rare cards by collecting certain stadiums and head coaches, and some of them pay out a large amount of coins and nice rare cards that may help you with other collections. A lot of people are willing to pay for the cheaper cards to finish their collections instead of purchasing another pack, if they are looking for a specific card to finish their collection.