One of the most important tips to insulate a crawl space is to insulate the exterior walls around the masonry instead of the underside of the above floor. This is even more true when pipes or heating ducts pass through the space.
Use unfaced fiberglass batts when insulating the walls unless there are problems with moisture in the crawl space. When insulating walls, it is important to wear gloves, a long-sleeved shirt, eye protection and a dust mask. The insulation is best cut to extend from the mudsill down the wall and to about 2 feet out to the floor. Secure the insulation with 2-by-2 cleats by holding each cleat where the end of the insulation is, and then drive nails through the cleat and into the mudsill's edge.
To hold the insulation batts in place, it is possible to place a 2-by-4 or a couple of bricks on top of them. It is also possible to cut separate pieces of insulation to fit between all of the joists and then press them up tightly against the rim joist. Other suggestions to insulate the crawl space include sealing the subfloor to keep drafts out and insulating the plumbing and air ducts. Adding a vapor barrier is also an option to insulate the crawl space, especially in cold climates.