The type of gear used depends primarily on the type of music being played. Genres such as house, techno and trance usually don't require the DJ to scratch tracks. Scratching is when a DJ takes a vinyl and moves it up and down while it is playing, creating a scratching effect. However, in hip-hop music, scratching is in a lot of songs and a hip-hop DJ usually incorporates scratching into the music. Pick the genre of music you plan on playing and choose the gear accordingly. For most styles of electronic music, the emphasis is on the blending of two tracks and its effects. Therefore, a MIDI controller and a computer are considered to be more important than a turntable with vinyls. Determine the effects you want to achieve and pick the gear accordingly.
Equalization is an important part of DJ mixing. A DJ mixer controls the equalization of a track. Equalization refers to cutting out certain frequencies in order to create a balanced mix. On a DJ Mixer, there should be three knobs labeled bass, "mids" and treble. The bass knob controls the low frequencies. The "mids" knobs control the mid-range frequencies. The treble knob controls the high frequencies. As a DJ, actively pay attention to how the mix sounds. This is achieved by cutting or boosting frequencies from one track that conflict with frequencies on another track. Use the headphones to listen to how the mix sounds before playing it back to the crowd.
Select songs for the music set that flow well together. A good way to do this is to ensure all the songs have similar tempos. The song selection process is the hardest part of a disc jockey's job. Selecting songs that flow well together and encourages the crowd to dance requires a good ear. It's also important to pay attention to the type of venue or genre for which you plan on playing and select the songs to match the venue. Putting together a "techno" song list for a hip-hop crowd won't encourage dancing. Put together several different programs based upon the genre or venue for which you play and use them accordingly.