Being relatively high on web searches, due to lots of gigs, and also very affordable, I have found that it helps to book early. You usually want to book the DJ you want about 6 months ahead of time to play music at your wedding reception. This gives you plenty of time to plan and do what you need to do.
Also, another tip. Think about priorities. Before you start planning your own wedding, what do you remember about one of the best weddings you have ever gone to? Usually it was great fun (entertainment) and/or the food. If the top two things your guests will remember are entertainment and food, make these your top priorities.
Do your homework. Find the Entertainment and the food first. If you know exactly the band or DJ that you want, and/or the catering company you want, get their available dates and then start looking for the best place. Many brides book a hall on a certain date, only to find that the DJ that they really wanted or the catering company couldn’t accomodate that date. I have had many customers a year ahead of time book me BEFORE they even knew where the hall was going to be, because they liked our product and also our price.