The first step is to set your clippers at the highest guard. If there is an adjuster on the clippers it is suggested that you keep it on the highest setting. If you are not getting the desired results, switch to a lower level. The setting of the guard may need adjustments until you finally get the desired length of hair.
Comb all the excess hair, cut it, and then switch the guard to a lower setting.
In order to get a straight cut, it is imperative that you imagine a straight line in your mind while cutting the hair on the sides. After going all around the head, you then need to comb the hair down.
You need to keep switching the guard and then combing the remaining hair downward. Keep repeating this process until you reach the bottom of the taper.
In the final step, in order to see the taper fade, you need to brush out the hair and comb. If you see that the hair is cut uneven from anywhere, do not panic and start the process all over again, keeping a straight line. However, this problem will most likely not happen if you set the guard right from the start, knowing what length of hair you want.