A lot of arguing over fishless cycling, not a lot of clarifying it to the person who's killing fish by not doing it right. Shame on you guys. You're actually causing the suffering you're trying to prevent.
Anyway, @ original poster:
Fish excrete ammonia. Ammonia is highly toxic. There are bacteria that convert ammonia to nitrite, which is also toxic. There are bacteria that convert nitrite to nitrate, which is relatively nontoxic.
The bacteria have to colonize before your aquarium is safe for fish. As a rule of thumb, they double in population approximately every day, as long as there is food (ammonia or nitrite) present for them. So, you have to make food available for them by adding pure ammonia in water, available at ace hardware in a 10% solution.
It typically takes 6 weeks to establish these bacteria. You can greatly accelerate the process by seeding the tank with filter material from an established tank.
Drying out will kill the bacteria. Do not allow your filter material to dry out.
Chlorine will kill the bacteria. Do not expose your filter to chlorinated tap water.
If you do not want to fishless cycle, start off with a VERY LIGHT bioload. In a 10 gallon tank, this would probably mean one sparingly fed 2" fish, or a couple 1" fish. Use hardy fish.
Higher temperatures accelerate the growth of the bacteria. If fishless cycling, set heater to 86*F.
Seachem prime will detoxify ammonia and nitrite in an emergency, without making it unavailable to bacteria.