How much direction should we give the dj for our wedding?

Every DJ wants some direction but any good DJ can take a short list of song requests and use that you formulate what type of wedding music you want. I would not go over board with the request list, I would say a good rule of thumb is around 30 songs. This should consist of the must have songs you want and songs you definitely don't want. You can also just let them know they types of music you want and they can run from there. The best DJ is one that does not play from a list, he is the one that takes the suggestions you gave him, feels out the crowd reactions and figures out what to play next.