Start by scanning a real ID. Only work with numbers and letters that you can copy and paste from the ID itself. If you use Photoshop's text tool, the numbers and letters that you add will end up looking different.
After you've printed the ID, the hardest part is finding a laminate that matches your ID. Since these are different from state to state, you'll have to do some shopping to find the best material.
As a tip, try first to show your ID to the doorman through a plastic window in your wallet. 9 times out of 10, they won't ask you to remove it.