What about the science of how the dice are actually made? When I open up my dice bag and pull out a hand-full of d20s, no two are the same. Some have sharper edges, others are smooth, some have large numbers, others have small pips. Does the science of how the dice are made have an effect on the outcome of their rolls? In doing my research, I ran across a company called Game Science which seems to confirm most of my suspicions. According to the owner's 2 videos (part 1, part 2), dice are put through a tumbler up to 3 times to add color coatings and remove blemishes. He then took 20 d20s and made 2 stacks of 10 with the first group stacked with the 1s facing the 20s and the second group stacked with the 9s facing the 12s. One stack was 1/4 of an inch taller than the other! The process of running the dice through the tumbler caused them to actually be egg shaped.
Because the dice were shorter when stacked on the 9s and 12s, they will have a higher chance to roll a 9 or 12 than rolling a 1 or 20. This is due to the distribution of weight of the dice and the location of its center of gravity. He goes on to explain about casino dice having a specific weight and size (within a tolerance of 0.0005 of an inch). The edges of the casino dice have the sharp edge to keep it balanced and the center of gravity in the actual center of the die. How do the sharper edges change the way the dice roll though? Well, the more rounded dice tend to roll farther and longer because the smooth edges allow less friction from the surface they are being rolled on. The sharper edges cause more friction and stop the dice sooner. That along with the center of gravity being at the actual center of the die, leads to more randomized dice rolls.
I went in search of some Game Science dice and found them at my FLGS (friendly local game shop). I haven't used them extensively, but they do appear to give a more random outcome than my rounded d20s. To help randomize my rounded d20s, I've also started using a dice tower (or dice boot). It seems to do the trick as well, eventhough it isn't as fun as tossing the dice on the table.
In conclusion, I suggest you make up house rules to cover the problems however you choose, but also, be weary of the dice being used. If you're constantly rolling 1s, teach that d20 a lesson and put it in timeout. If you're more mathematically inclined, give each of your d20s 50 rolls and keep a log of how they land. You never know, you may have one that consistently rolls high and didn't even know it!