I hired a DJ. Now, how do I make sure everyone is dancing?

 Here are some tips!

1. Get on the dancefloor!  If you get on the dancefloor, people will follow.  After all if you invited them, and they came to party with you.
2. Create a list of past favorite songs you like.
3. Listen to the radio!  Become familiar with the current popular top 40 music, and figure out songs you like and can dance to.  This ties into rule 4.
4. Make sure you tell the DJ the music you like!  Include your past favorites as well as the top 40 you like.  This will give the DJ an idea of what genres to play.  If you know a certain group of people like a certain type of music or song, make sure to tell the DJ as well.
5. Spend some time drinking (if you drink), socializing, or maybe go outside if you smoke, but then get right back to the dance floor.  The DJ gauges what songs are working and what songs are not working, but this only only happens if the guests are on the dance floor, or inside the building.  If you hang out by the bar or go outside all night, the party follows you.
6. Encourage guests to requests songs they like, especially if they know these songs crowd favorites.  Discourage guests from making requests that suck (especially if the songs not danceable!).  Instead, get these guests to make requests right away, before the dance.  Make sure to ask the DJ to play these requests that are not necessarily danceable before the dance actually starts.  This will keep the guest requesting the songs happy, and it also acts as a good warm-up for the crowd.
7. The music should be loud and clear.  If the music is not loud enough, inform the DJ.  If the music sounds too loud and distorted, tell the DJ to turn it down. A good sound system will be loud, and clear. 
8. Move guests that will be bothered by loud clear music away from the speakers.  If not, these people will eventually move on there own or leave once the party has started.  If you have a younger audience then no need to worry.
9. Move guests that will be bothered by the light show.  Most lights will not be aimed into the eyes guests, but depending on the age, you might get some lights that are cool for a younger group, but annoying to an older group...  A table of people not dancing "looks" better at the back! lol...
10. Get those guests that are annoyed by the loud music, and/or those guests who are complaining about the bright lights to join in the dancing.  Request a song they'll like and get them on the dancefloor.  Chances are they want to party with you also!