12:10 p.m. on April 11, 2011 (EDT)
You say that your heel rubs up and down in the boot. That, of course, is the reason for the blistering. The reason for the heel movement is that your foot and the boot are different shapes and sizes, which is why you see the advice here on Trailspace so often of the necessity of having boots (and packs) properly fitted by an experienced and trained bootfitter. So, what to do now?
First step is to wear proper socks. This means an inner pair of light wicking socks, made of something like Coolmax, plus an outer pair of insulating, cushioning socks, preferably Merino wool. These will be fairly heavy to provide cushioning. FITS and Smartwool are good brands. Both the inner and outer socks should fit smoothly, with no bunching. You already may be doing this.
Second (or maybe first) is to use proper insoles in your boots. Many years ago, bootmakers stopped putting proper insoles in the boots, since people's feet are so different, and a number of good after-market insoles became available. I, along with many others here on Trailspace, use Superfeet. These have a heel cup that may in itself solve the problem. There are other brands, but the "green" Superfeet are designed for hiking boots. Insoles do wear out, so will need to be replaced from time to time (few hundred miles of hiking). Some people need to go to a podiatrist to get a custom orthotic.
Another thing is proper lacing of the boot. Many, if not most, people (and way too many store clerks) do not know how to lace boots. If done properly, the toe area will have lots of room, while the heel will be held firmly in place. You can ensure that the upper does not loosen by back-looping the laces on the hooks above the arch of the foot and up to the ankle (that means doing a half-hitch on each hook as you tighten the lace).
Proper breaking in of the boot also helps, once you have solved the proper fit question.
If all this does not solve the problem, you will need to find a trained, experienced bootfitter to do some minor alterations to the boot (stretch a few places, pad a few places, etc).
This doesn't help on the trail. Since I learned many years ago about the importance of proper boot fitting, I have never had any blister problems. But I have had to treat blister problems out on the trail. I do not find moleskin to be very satisfactory, though others swear by it. The thing is to catch the "hot spots" very early, as soon as the discomfort is noticed. Clean socks, smoothed, are very important. Dry feet are important (use good foot powder like ZeAsorb). Wet socks will slide around a rub raw spots, as will dirty socks or socks bunched up. I have found that Spenco and 2nd Skin work much better. Also to hold the tape (including moleskin) in place, clean and dry the area and use a little benzoin (you find this in the drug store in the foot care section, or even at REI or EMS) - this helps even with very sweaty feet.
And of course, a dozen others will now chime in with all sorts of advice.