Reply to Booking Advice

So I recently started working (DJ'ing and promoting) at a very large new club in my city and I just got the go ahead from the owner and the creative director to start looking in to booking touring DJs for one of my evening s (Sunday evening , progressive themed) and I need a little advice.

Before this I have only booked local DJs, which is fairly easy, you just send them a message on facebook with a date and usually they go for it but that seems a little crass for contacting a DJ's agent who I don't know. So I'm left wondering what's the best way to approach a booking agent who has more than likely never heard of me or my club and what type of information to include in my email. I'm also worried about being ignored because I sound unprofessional or knowledgeable so I have come to you for advice.

How do you guys reach out to agents? What type of information do you include in your emails? And how do I sound like I know what I'm doing?