One thing worth noting: If you have soffit vents, be sure they stay open. They make a plastic vent channel that staples to the rafters to keep an open air channel to the soffit, and it extends above the insulation. You could probably be more mustachian, and make something similar (1/8" or 1/4" thick MDF, etc would probably work well).
Good attic ventilation is important to reduce heat to keep the house cooler, reduce moisture, extend shingle life, etc. If you live in a hot day / cool night dry climate like we do in Colorado, it also lets you install a whole house fan so you can give your money sucking A/C unit the big fat FU. :-)