Water (as covered by bstpierre) is my first thought, and his comments about seed quality are good - this could easily explain very poor germination rates.
Which kind of pepper seeds? Some species cultivars are harder to germinate. Most varieties such as bell peppers, jalapeños, etc are in the easy category.
Soaking the seeds for a few hours in salt petre (Potassium Nitrate) is recommended for the harder to germinate varieties. I do this as a matter of course but should probably do a comparative test - I'm not convinced it has a great affect.
Finally, I plant at a much shallower depth, sprinking the potting compost over the seeds to cover them up. Due to vagaries of my technique and that I push exposed seeds in with a finger, some definitely end up 1+cm down and still germinate (I don't know what percentage germinate at this depth).
If there are any kids reading all this, the above could make a good junior science fair project!