Tom's crawlspace vapor retarder recommendations are good and the rest of it is sound, but it's not necessarily what you need for your particular house. There's a lot of stuff that goes into this, more than blanket prescriptions. What's the house design? What kind of attic.....overhead, side crawlspaces (like a cape cod), any vaulted ceilings, locations of ducts....all sorts of stuff. I've found that most insulation contractors are the worst advisors about what to do; they have a product and they sell it. Most, not all, but most. There's ancillary issues of tightening a house up with foam, primarily indoor air quality. We've been finding that the one's that are tightened up like a foam beer cooler can have serious air quality issues that require an ERV or similar ventilation system to introduce fresh air. So, it's not complicated, but it's not always a simple prescription. And, I've found the DOE pamphlets to be essentially correct but almost always so generic as to have little actual value in prescribing what one ought to do in a particular structure. Put up a simple picture of your house as a start.