From www.favim.com

The first thing that I have to say about reading a crowd is that it is a skill. Though some people pick is up faster, it is something that comes with hours of DJing and practice. However, I can provide a few insights about how to practice and how to “test” a crowd. Though I wish girls walked into the party with words on their heads that say “I love country” or “I love house music”, this is generally (and I would hope) not the case. In addition, its also frowned upon to go up to a girl and say “hey cutie what do you want to listen to today?” Though some girls would like that, it’s just not the thing to do. This is why DJs put out “tests”. Though the listener doesn’t always notice, many songs do not usually play for more than a minute and thirty seconds. This is important to a DJ, especially when testing a song. Of course it is important to be conscious of transitions. This testing is sometimes what I do when I have confusing or hard to read crowds. For example, I was DJing a party the other day and it wasn’t up to my standard of “crazy”. In hopes of turning the party up, I played a throwback “bar-mitzvah” style song and it was in instant hit so I stuck to that genre. If it didn’t work I would have waited about thirty seconds and then changed the song. Sometimes it’s just simple trial and error that works the best.