How can I become an organ and tissue donor?

It's easy. It's a great idea. First let your immediate family know of your wishes. You can check the box on your state driver's license. You can ask you local organ procurement organization, if they keep list. You can even sign up on facebook. http://www.nytimes.com/2012/05/01/technology/facebook-urges-members-to-add-organ-donor-status.html?pagewanted=all.
Register. You register with your state. Go to organdonor.Gov and you can register online.