One of the key components of an effective home energy assessment is infrared thermography. Infrared thermography (or infrared imaging, infrared diagnostics, a rose by any other name...) consists of a thorough visual inspection of a home, including the basement, attic, and all the nooks and crannies, with an infrared camera or another infrared assessment device. It essentially takes the guess-work out of pinpointing the drafts and the leaky spots within a home — registering, as it will, the exact temperature of various spots within the home, and, depending on the device used, providing you, the homeowner, with a precise visual representation of the imperfections in your home's thermal envelope. So if, after the energy assessment, you forget where exactly it was you were supposed to caulk, you've got a big stack of pictures to show you exactly what spots need air sealing or insulation work.
If a picture, as they say, is worth a thousand words, an infrared picture could very well be worth a thousand bucks, because it reveals the spots where your house is wasting energy (and money), and gives you clear directions for fixing them. Some of the imperfections in your home's thermal envelope will be obvious: around windows and doors, for example. But chances are, there will be some big surprises, too; and that's part of what makes infrared imaging so valuable - you might discover that the constant draft in your living room could be taken care of with a simple bead of caulk along the baseboard, or that your perennial ice dam could be forever prevented by insulating a hot water pipe in the attic.
One last thing to bear in mind when scheduling an infrared assessment is that for best results, there needs to be a temperature differential (delta T) between indoors and outdoors. Recommendations as to precise numbers differ, but you should talk to your assessor about an ideal differential for your region, climate and house.