The tricky part of hanging double doors is that they have to meet in the middle. After hanging each door, check to see how they come together. It's seldom perfect the first time. If they overlap by more than one-eighth of an inch, you'll need to plane some off both doors. For smaller overlaps, only one door needs to be planed and sanded until you get a perfect fit.
For more on doors, consider:
10 New Uses for Old Doors
How To: Install a New Door
Know Your Door Styles: 10 Popular Designs