Here, read these links:
http://www.aquariumadvice.com/forums/f12/fish-in-cycling-step-over-into-the-dark-side-176446.html
http://www.aquariumadvice.com/tips-and-tricks-for-your-fastest-fishless-cycle/
The first one is about fish in cycling, the second is about fishless cycling. To cycle a tank you need to get some level of ammonia, and have bacteria in the tank (that get there through the air) to "eat" the ammonia, and make nitrites, which is "eaten" by another type of bacteria that produces nitrates. Ammonia and nitrites are very bad for fish, and levels over .25 ppm of those are bad and can cause permanent damage (given enough time in that water). Nitrates are much less toxic. Nitrates should be under 40 ppm, but under 20 ppm is best. Nitrates are removed through water changes.
A fish's waster produces ammonia, which is the source for fish in cycling. For fish in, you just add fish, test daily, and do a 25 % water change when water gets above .25 ppm for ammonia or nitrites, until you consistently get 0 ammonia, 0 nitrites, and x nitrates. Then, you are cycled (you have built up enough bacteria to "consume" the amount of waste produced by your current stock of fish. This is known as a bioload, the amount of waste a fish produces), and can add more fish, a few at a time.
Fishless cycling uses a source of ammonia (pure ammonia [bottled], a raw shrimp [the kind we eat], or fish food), try to get ammonia up to 4 ppm (but less is okay), and then just add more ammonia when it drops under 4, and do a water change when ammonia or nitrites somehow get over 5 ppm. Once you consistently get 0 ammonia, 0 nitrites, and x nitrates, you are cycled, and can add your whole stock at once. If you don't add your whole stock at once, say add only 5 fish, and then wait a week, you cannot add your whole stock then, as the bacteria will die off until there is just enough ammonia produced for all of the bacteria to eat. While fishless cycling you should test at least every other day.
Parameters are the level of certain chemicals and substances in your water. The most commonly tested are Ammonia, NitrIte, and nitrAte (we often capitalize the I and the A in the respective names because the names are alike but the substances themselves are not in the slightest). pH is also an important factor. pH stands for potential hydrogen, and it's pretty confusing but basically the scale is from 1-14 with 7 in the middle. The lower the number, the more acidic the substance. Lemon juice, I believe, is around a 3, whereas ammonia is around 9 (not too sure on that). Water pH varies, and it can effect fish. Some fish are not very hardy, or are more delicate, like Discus. These kind of fish often require a specific pH that is most like their natural habitat. But for most fish, the most important thing is the the pH remains stable, because fluctuation can cause stress, which may lead to disease, or death. Ammonia and nitrite are fairly different but the deadliness is fairly similar. The general rule is that neither should be allowed to exceed .25 parts per million, or ppm. Nitrate is far less toxic, and for most fish less than 30 ppm is perfectly fine, but for some, especially saltwater fish, they require far lower concentrations, like 10 or 20.
