Now that you have made the deal and the booking is confirmed, it is time to prepare for the performance itself. There are a few things that are important before you can start your routine.
Know Your Music
Unless you are playing a live set or a headline show, you don't need to know in which order you will play your songs. It is better to be flexible as a DJ. Half the time, a set will turn out completely different than what you have expected. It does help if you know the music in your library well. And it also helps to know which songs mix with other songs and which don't sound great together. It is always good to have a few new tracks but don't bring along too many new tracks. You often won't be able to estimate what they'll do for the dance floor unless you have heard them enough. This is again about mastering your skills. As a DJ, it all starts by knowing your music. Compare it to a vocalist who doesn't know the lyrics.
Know Your Timeslot and Role
As mentioned before, it is essential to know what your time slot is and your role in the night. Build-up sets are probably the most underestimated time slots of the night. You can learn a lot from them, and they are a great way to learn the dynamics of a dance floor and try out your own tracks. If you keep the crowd on the dance floor and in the vibe, you will be respected by the talent buyer or promoter, the crowd, and the headliner. As a starting DJ, you surely want to rock the crowd right away but you will be better respected if you know your place in the lineup and your role for the location and event. Nobody likes listening to loud, noisy music while having a conversation at a cocktail bar. In a way, the primetime set is easier. You should bring the crowd from a climax to a climax. Just remember that sometimes climaxes come out better when less euphoric songs introduce them. It also makes a difference if you're playing a short or long set. No one likes listening to climaxes for three hours. People get tired of it. You always have to think about the storyline of the set.
Know the Line-up
Another essential thing to think about is the other artists on the line-up. You should always play the music you believe in, but it does help if you play something compatible with the music and the night. If you're opening before a future house DJ, it probably won't make sense to play a techno set, and If you are playing after a techno DJ, it won't make sense to play a future house set. This is also something you should think about before making a booking.
Know the Venue/Festival and Its Crowd
An excellent way to prepare for a performance is to gather information about the club, party, or festival. What does the venue or stage look like, and what does it sound like? Whom are the people frequenting this place, and what do they usually listen to? The best sets are symbioses between the crowd and the artist. You need to know how to please them to lure them into your world. Long story short: doing your homework can benefit you and help you stand out.
For Non-DJs
For non-DJs, I recommend you rehearse your show repeatedly until you can do it with your eyes closed. Everyone has to work together seamlessly. Record your rehearsals and see what can be improved.