Do your research. If you go to any functions where there's a DJ company working, go up and talk to the DJ. If he/she's an employee, ask what they're like to work for. If he/she's the boss ask about job opportunities. Or if you know of any companies that have regular gigs in a pub or club do the above as well. If you're new to it all but have a keen interest in getting work, working for a company could be a great way to start in the industry.