The idea is exactly as the title suggests, set aside a chunk of time (one day, several evenings, whatever you have) and go through their to-do list. They make categorical breakdowns of how you can save money, where to do it, and how much an average tester saved.
Getting a library card saves you $70, but that's assuming you only buy 4 hardcovers a year. Heck, everytime I simply set foot in a bookstore I'm out seventy bucks. The home energy saver advisor site was excellent (under cut heating and utility costs). One caveat, for New Yorkers (or anyone in an apartment building) filling out the form might be a little hard since you might not know things like the thickness of your ceiling's insulation, but do your best. The end result's suggestions on upgrades and how much you can save is easy to sift through regarding what is relevant and what's not. Plus, an energy audit is a great thing to pass on to a Co-op board or a landlord :)