Buy a set of direct-drive record decks (known as turntables or decks), a mixer, some speakers, and some vinyl records. You will also need some slipmats to learn to do some "mixing" and "scratching." Set up the equipment as the instruction manuals suggest, with the mixer positioned between the two decks.
Practise mixing. The basic art of being a DJ is being able to mix records. No matter if you want to DJ house music, hip-hop, or drum 'n' bass, the rules are the same. Set a record playing on the left-hand turntable. The sliding switch on the mixer is called a crossfader. Keep it in a "locked" position. Then start a record playing on the right-hand deck. It will only be audible through your headphones, unlike the left-hand deck, which will be playing through the speakers. Get the right-hand record playing in time with the left-hand record, then slide the crossfader over to an "open" position. Both records will become audible.
Learn how to scratch. Scratching is more popular with DJs of certain types of music. Scratching is integral to hip-hop DJing, for example, but only occasionally used by dance music DJs. The basic idea behind scratching is to have one record playing while you "mix in" the sound of the other being pushed back and forth. To scratch, you need to use both hands, one to manipulate the record, the other to move the crossfader back and forth. This takes a lot of practise to do well. Basic scratching techniques include the "baby scratch," the "stab," and the "chop."
Buy a decent computer with plenty of RAM and memory capacity. Now that you have mastered DJing, you are going to want to record a DJ set and send it off to studios to let them know just how talented you are. A decent computer is vital since it replaces the need for other more expensive recording equipment.
Download or buy some music software for your computer. Virtual DJ pro is a popular choice for PCs, and it's free. You can also buy more comprehensive music software packages from electronic retailers, but to start with Virtual DJ will let you do the basics.
Hook up your your mixer to your computer and start recording your turntable skills. Experiment with new types of scratching and try mixing different styles of music together. The more versatile you are as a DJ, the more likely it is a studio will want to employ you.