I just want to Echo what Gary has said. Over the years when i've been training D.J's one of the most common problems, is their own opinion of music conflicting with a dancefloor reaction. For instance, there are a few people who like the Mad World re-release by Gary Jules - however as D.J's we wouldn't play it since it's a dancefloor killer......and bloody depressing

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With your own example - Footloose. Yep, better than Gary Jules

, a popular track that most people from that era will remember, however the main thing to consider is its tempo. This is a very fast track and would probably not appeal to the dancefloor masses. In other words a good radio / driving track but not a dancefloor classic as far as us mobile's go. However, having said that, you may find that it works reasonably well at another gig in the future

, all audiences are different.
Reading and understanding a dancefloor is a skill that can take some time to perfect, it probably won't happen overnight. The best thing to do is read some tips on music playlists here on DJU where other D.J's post what they play during a typical function, and then stick with the relatively safe stuff to encourage them onto the dancefloor...and yes, sadly that often means a lot of cheese and playing a lot of predictable material, but if it gets them dancing than thats half of the battle won.
Requests Slips are the D.J's friend!. They give you an indication of what the audience will like, and can be of great help during the early part of the evening when you are looking at the age range of the audience, scratching your head and wondering what to start off with. Obviously, if you at a Function then ignore the odd request for Marilyn Manson, Linkin Park, Eminem etc that the only 15 year old in the building would like to hear!. Request slips are great, not only do they encourage your audience to get involved, but if the majority of requests come back as being from the 70's era, for example, then you would realise that the majority of the crowd are 70's fans and it would be a relatively safe bet that it would get a favourable dancefloor reaction. Consider getting some slips printed / photocopied with your roadshow name, contact details and a space for requests, and then distributing a few to each table and around the bar area before the guests arrive.