Most reception halls have the order for you available. In the past weddings I've been to, the first thing after the guests were in the sitting arrangement was to allow the bridal party to enter. This is done by the MC introducing them in the order that they entered the church. So, first Bridesmaid/groomsman couple, and so on. The Best Man and Maid of Honor come last, and finally, you introduce the new Mr and Mrs XXX. At this point, they dance their first dance, you announce the song. Half way through it, you ask the bridal party to join, finally the rest of the guests. Some weddings have right after the Father/bride dance and the Mother/Groom dance. Remember to announce the song their dancing to. The last wedding I went to, had this after the main meal. Right before or right after (I've seen both) of the cake cutting, which is after dinner, you have the bouquet/guarder toss. The new couple usually opens the dance floor. The order isn't set in stone, and you can change it as best as it suits you.
If you want a good check list with all the details try: http://www.thedjforyou.com/Reception%20Itinerary.htm