Learn the traditional Bridal waltz or something a little more flamboyant. You may elect to join group lessons or have private tuition.
Will lessons be just for the bride and groom, or the entire bridal party?
Many studios will personally choreograph a wedding dance for you, to your choice of music.
Research and meet with several instructors.
Decide which dance style to learn.
Decide which company to use.
Have fun with it!