I recently hung my first interior door at an old house I am fixing up. I used a new product called a Quick Door Hanger instead of the usual wood shims. The hanger kit costs about 5 dollars at Home Depot. The kit contains 6 brackets that screw to the prehung door frame, 3 on each side. You put the door into the rough frame opening, check for level, then drive 6 drywall screws through the brackets into the rough frame. Done in 15 minutes and no fiddling with shims. There are Yoo Toob videos of the product in action. Makes the job easy for a newbie, half fast carpenter.