There are can be several reasons for heel lift.
1. The boot is too big. Pull out the liner, pu your foot in the shell with your toes touching the front, there should be 3/4" space behind your heel. If there is more than 3/4", you can go to a smaller size boot, or use something to fill this space, like the "butterfly" mentioned above.
2. Small ankles, if the size is correct, sometimes you just can't get the boot to tighten properly, an Eliminator tongue can help.
3. Narrow or skinny feet, you will need to take up space, high volume footbeds can help, or tognar sells a narrowing pad that could help as well.
4. Crappy boots, some boots just arent designed properly, and will not tighten up in the right areas, not much can be done here.
If you have expensive boots, spending some time at a boot fiiter is worth it.
I have the narrow ankle problem and use an Eliminator tongue, works great. I also use an aftermarket foot bed. Sperfeet are good, Sole (yoursole.com) are better.