Decide if you want to play music in clubs or play your type of music in clubs. It’s best to start with a wide mix of genres then as you make a name you can narrow down to the genre you the most passion for. Like Terry said, get some business card made. I carry two types, one for my mobile DJ work which promotes me and my DJ partner and a personal card which promotes me as a House DJ. I’m now leaving the mobile work to concentrate on getting club/bar work playing the music I have a passion for so I’ve bought some cheap memory sticks to put my audio mixes on and a video of me mixing which get handed to club promoters and managers. For a what equates to less than a £1 per handout I think it’s a great way to promote. Use facebook, Google+, Mixcloud (as there no limit on the mixes) etc. Promoting yourself and getting your foot in the door is not an easy road and will take hard work, a thick skin and perseverance.
Get out to the clubs get talking to the DJ’s, the bar staff, the door staff, the events manager, the bar manager, the clubers. If your DJ friend is doing any other gigs go with him even if you don’t get to play, introduce yourself to the promoter. If you do get to play a 30min set all the better. I always carry my own USB stick (16gb) with music on just in case I get a chance to play at a party I’m going to as most DJ’s use a laptop these days and if the have CDJ’s with a usb port even better.
A lot of my mobile DJ work I got from a signing up for PLI with a DJ website for the £49 it cost for the insurance I made my money back and a profit in the first 2 weeks from the referals they passed on. I’ve now found a similar site for DJ’s who want club work. I got turned down when I first applied but I didn’t give up they’ve now accepted my application so for a 6mth subcription at £89 pounds I think it’s worth it. I’ll let you know how it worked compared to me promoting myself