How do I prepare doors to be hung?
Do you have access to a router?  You'll save yourself a huge amount of time if you buy a hinge mortise template (like this one from HD) and use the router to cut out the mortises:



They attach temporarily onto the edge of the door, and you use the router in the large opening to cut to the correct depth.  Once you're done, take the template off the door and screw in the hinge plates.  Done!