According to the literature only 20% of the population has "normal" feet. Others have non-standard feet which can cause problems with foot or boot fitting, or cause one to suffer from sore knees, hips and/or lower back.

Every step you take puts 2 times your body weight on your foot.
Running puts 3 to 4 times your weight on each step you take.

If your feet become sore from running or walking, you might be tempted to try orthotics--custom-made shoe inserts that take the place of insoles. But orthotics can be expensive and might reduce a shoe's cushioning. Consider whether your problem could be solved with new shoes or a different category of shoe (cushioning, neutral, or stability and motion control).
See Athletic Shoes under products.

Pronation:
The outside part of the heel makes initial contact with the ground. The foot "rolls" inward about fifteen percent, comes in complete contact with the ground, and can support your body weight without any problem. The rolling in of the foot optimally distributes the forces of impact. This movement is called "pronation," and it's critical to proper shock absorption. At the end of the gait cycle, you push off evenly from the front of the foot.

See videos from medical motion
and RunnersWorld: (normal, underpronation, overpronation).

If your feet pronate (roll inward) excessively, a stabilizing or motion-control shoe might minimize the problem. And if your feet don't pronate enough, a cushioning shoe that emphasizes shock absorption might be best. Overpronators typically have a low arch, underpronators (supinators), a high arch, and neutral runners fall somewhere in between.
Source: Athletic shoe guide from Consumer Reports

Analyze your feet:
Wet your feet and stand on a flat surface that will allow your footprint to be seen. Comparing the footprint with Figure below gives an idea regarding pronation.

Some people will have neutral feet when standing and walking without weight, but will over-pronate when running greater than 3 miles or backpacking, so you need to examine your old shoes to see how they are wearing.
 
Source: Runner's World Forums and DukeHealth.org

You can get off the shelf support insoles to replace the insoles that came with your shoes or boots such as Spenco or Superfeet. You generally use the same ones whether you are pronated, Supinated or have other problems. Or you can get a podiatrist or chiropractor to measure you for custom orthotics at $400 to $500 per pair.

Foot Impression Techniques for custom orthotics:

One knowledgable foot shop told me they don't actually mold an orthotic to the impression you send in, but look at it and select a pre-made one from a rack.
At Advanced Casting Technology they recommend a weightbearing impression method.

Boot Doctors:
Many popular ski areas or destinations have a boot doctor who will modify ski boots to make them fit better.
Cosmo's Custom Footwerks & Golfwerks - Truckee CA
Jim Schaffner at the StartHaus, 10990 Donner Pass Rd Truckee.

Links:
Athletic Shoes here under products.
Tognar Ski Snowboard Boot Fitting Fit Repair Tips
Insoles : Shoe Insoles : Foot Supports : Foot Health : Footsmart.com
Standard Orthotic Adjustments & Foot Biomechanics - Orthotic Shop
Pronation, Explained: Info from Runner's World Magazine
- Motion Analysis, Video Motion Capture and Gait Analysis - Medical Motion