I suggest using shims on both sides or the door. Studs tend to be twisted quite often and if you nail the door directly to a stud the door may end up "loaded." This happens when the jambs are riocked one way or another. Also, use 2 1/2" trim nails for installation, not screws.
Set the prehung door in opening. Use level to check top/sides. If the bubble is off on top, trim doorjamb as needed to correct.
Set your first shim on the top hing side. Nail just BELOW the shim. This will hold the door in place and allow you to still adjust that shim until everything is plum. The most important thing is reveal and sometimes doors are better set by measurement than level. If the door is 2" away from a wall and that wall is out of plumb, if you set the door perfect plumb it will look off becasue the wall is off. Once you are happy with your reveal, nail the top shim. Then set the other 5 shims and nail off. No need to ship the top.
Like I said before, it is more important to make the door look perfect than be perfect. If the framing is off in a house, and it often is, it is the trim carpenters job to make the doors apear right. Anyone who comes into a house and sets everything by level when the walls are off level is a hack.