Hiring a professional DJ should mean that you are allowing them to choose which music to play and when. If you have chosen somebody with experience and knowledge then you should be trusting in them to draw on what they know to rock the party.
With that being said, it is also vital that you give your DJ a list of songs or artists that YOU and your family are likely to enjoy. This gives me a starting point to engineer a unique reception that is tailor made for you and your crowd. I have sections in my online planning form for 15 high priority songs (15 is about how many songs I can play in an hour) as well as space for as many other requests as you wish to make.
I pride myself on playing amazing music that is not typically heard at weddings but still fits within your plans and the dynamic of your crowd. This really draws people into the event making the energy skyrocket. Guest requests are a big part of what can make this possible.
Going from table to table during cocktail hour and dinner to introduce myself and ask for requests is key. This not only gives your guests a chance to get to know their DJ a little better but it also opens the door for great input. This is input that clues me in to what will make them rush to the dance floor.
Your guests will remember the fun they had at your reception long after every other factor is forgotten. Don't forget to add those music requests, they are what will make your reception not just fun and unique but also totally unforgettable.