Install the hinge side plumb in both directions. Take extra care on this step. Then uses some blocks to hold the door up at the proper level when you put it into the hinge channel. Take plenty of time to ensure you have the correct margins all the way across the top and along the latch side of jamb. Now put in the screws in the hinge channel. Buy some extra self-tappers and use about twice as many as come with the door!
When drilling for the latch, start with a small pilot hole, and work up in 2 steps to the final size...3/8 or whatever they call for. You will end up with a neater hole.