pay attention to the other djs. notice how they do all the confusing things.and most of all, listen to as much music as possible. download any random song or ask a friend some songs they recommend.
I am hoping you are saving your monies because to be a top notched D/J .. you will have to invest in lights, music , promoting material and fliers and entrainment agent who can prove they are real because a lot of them say more than do! so be very careful!
First take a musical theory class. Get a cheap set of turntables and a mixer. The biggest part is understanding what music is in a technical sense.