It's the DJ's responsibility to know when all the events are supposed to occur during reception, like cake cutting, bouquet tosses, etc. The DJ's job is to work with catering, and know when meals are being served and when the milestone events are to take place. The DJ and the caterer should have this under control before your reception begins.
What about Chicken Dance, or Hokey Pokey?
Some people love it, some people hate it. But it's your wedding and you will know your guests better than the DJ. Let the DJ know your preference. If you hate these songs, you would hate to be surprised by your DJ playing them at the reception!
Technical issues to consider.
Everyone overlooks this, but it is an important factor when choosing your DJ. You are paying money for a professional and they better know their equipment. Ask them what speakers and amps they use. This is another reason why you need to ask the DJ if they do corporate affairs, because they may use the same high end audio equipment at your wedding.
You don't want them using home stereo amplifiers and speakers because they will fail under the volume of use. If the DJ's equipment consists of a "home-built mixer" and a hi-fi system you should start looking for another DJ! This kind of sound system usually doesn't last an entire event! They will produce problems and then you are stuck with a crowd and no music!