Hiring a wedding disc jockey is an important part of any wedding. You may not have a lot of experience renting or working with "DJ".
You should speak to / interview before hiring anyone. Just because a DJ does a good job for a friend or someone you know does not mean they are what you are looking for at your wedding. You can get more info of the wedding DJ from various web sources.
During the interview process, you should have determined what would you want to have happened during the wedding and reception and how you want them to interact. But before you tell the DJ what you want or expect to let them explain what they will do for you.
A most wedding disc jockey will follow a fairly set pattern. They introduced the bride. They will introduce and begin to dance numbers including the bride's father and mother dance.
You want someone who will actively keep things moving, someone with personality, some people who really know how to get the crowd involved and have a good time.
Anyone can sit behind a stack of speakers and equipment and "spin records", play songs. You really want a wedding DJ, Director of Entertainment, which will help ensure that everyone at your wedding and reception will have a great time.