Epic Games have kick-started a new campaign for the Gears of War 3-beta called "Never Fight Alone". Current players will be able to earn "Buddy Tokens" by taking part in a fight in the beta, which they then can send to a friend who will get an invite to the beta. You can also make tokens by doing various things, including buying Gears of War from Games on Demand or playing 20 hours of the Gears of War 3-beta.
The tokens will be around until May 4, and they will all be sent out by Microsoft before May 8.