I've noticed over the last few months the gap on the driver's side door has been getting worse and worse and now its off by about a quarter of an inch. What is the best way go go about adjusting the gap and a good way to ensure it doesn't get off again?

 

The bushings are probably shot. The longer you wait the more damage will become of the hinges.

Order a new set from top down solutions and be done with it. Then you can properly align the door.

 

Like Jr said, the longer you wait, the more damage you do. It will actually eat thru the brass bushing and into the door hinge. I had to put a spot of weld in my door hinges to close up some of the wear.