Summarize the following:
Depending on the venue and your experience and style as a DJ, a club may have a specific stylistic request for you, or you may have more freedom to play what you want. But whatever the nature of your agreement, you need to spend some time before the set sketching out a basic theme, with at least your first five tracks laid out.  Are you going to stick with straight-up club jams, or are you going to throw any surprises into the mix? Old-school disco fist-pumpers? Rock songs? Make sure you've got any swerves prepared for on your disc drive, or in your record crate. You can always throw the plan away, but at least you'll have something to start with and get a chance to read the crowd. If you drop a trance-beat banger and nobody moves, you'll know you need to switch up the theme. If the place goes wild, you've found your groove. If you've got your head buried in your vinyl crate and your mixers the whole time, you're going to lose them. It's important for a club DJ to pay close attention to what the crowd seems to be responding to, how they're reacting, and what the energy level seems to be in the room. It won't always be obvious, but a good DJ can learn to spot a crowd's needs before they're even aware of it themselves.  Watch for bangers. Some songs will get people pouring onto the dancefloor, which you'll need to follow up with at least 2-4 similar songs to keep the party going. After that, you might start slowly transitioning away from that style, but matching beats so people won't lose it. Watch for the exodus. Likewise, keep an eye out for clunkers. If you throw on something with vocals and all of a sudden people lose it, consider dropping back into your straight-up instrumental set. Find out what people don't like. If every other DJ's going to play it, you might think you're above that new Top 10 single, but if people want to hear the newest dance jams, you'll be doing the crowd a disservice not to play it. Try to stay abreast of the commercial dance music that people are likely to want to hear. You don't have to play the basic song, consider drop a remix or a mash up, or remix it live. Maybe make a few edits of the most popular songs before you go and drop those. Every crowd will be different, and crowds can even change over the course of an evening, or over the course of an hour. Some crowds will want to trance out to nothing but heavy-banging house all night, while others will want to hear some Jackson 5. Pay attention to what works and what doesn't, and have a steady stream of old-school dance classics at your disposal. Sometimes a crowd that skews "older" may seem like an obvious choice for wanting classics, but not necessarily. Any time you're DJing for a non-club type of club atmosphere, in which the crowd isn't necessarily dance-music enthusiasts, you're likely to win the dancefloor will some well-timed classics. People are out to have a good time, not to think hard about the heady and artistic set of experimental electronic dance music you're curating. Give them the music fix they need, get them to dance, and reflect their energy back into your mixes. That's your job. There's no such thing as "a bad crowd," but there is such a thing as a bad DJ. Good DJs can read the room and supply an appropriate soundtrack. People may dance, people may not dance, but it's your job to do the best you can to read the room and reflect the vibe.
Start with a basic theme. Watch the crowd. Pay attention to the charts. Know when to drop some old school joints. Try to keep everybody happy and in the moment.