In response to the question "what makes a good agency better than the rest ?", I've got a few comments based on my recent experiences in trying to book DJs.

They should know their artists and music styles. I promote predominantly techno nights and I am now fairly sick of emails/faxes/calls from agencies offering me DJs who play completely different styles. What am I meant to do with a DJ who plays jazz-house on a techno night ?

As well as the DJs and music, they should also know the promoters they are trying to deal with. I approached one giving details of our night, explaining capacity, budget, style of music and opening hours. They now continually send me details of oversees DJs who have got a booking fee that is between 6 and 10 times greater than our limited budget, and that's before I even add travel, accomadation and flight share prices to the equation.

It's also preferable if they have got some connection to, if not a love of, the scene, and aren't solely interested in getting their 10%. Some have point blank refused to shift on fee and commission, wouldn't pass on details to the DJ to let us talk in person. I later spoke to the DJs in question and found that they would have reduced their fee in order to help out a club that was only starting out because they love the scene and are more interested in spreading their music than making money. Their agents prevented these conversations from taking place, so both us and the DJs lost out.

That's just some stuff imho that makes some agencies better than others.
It might seem like a lot of negatives, so I should finish on a positive. I think the way Stay Up Forever do their bookings in house is probably the best way and I have nothing but praise for them and the way they helped us out.