Let's see according to my BEO...
Prelude - a bunch of songs for people to listen to while being seated
Mothers Entrance
Groom's Entrance
Bridesmaid's Entrance
Ring Bearer/Flower Girl entrance
Bride's Entrance
Major Domo Entrance
Unity/Sand Ceremony
Recessional
Moley! That's quite a few!

So you need to decide if you're going to have actual musicians or have a CD player. If you're having musicians, you need to get the sheet music to them if it's a not commonly known song. (I think Betsy had to do this with Ben Folds - "The Luckiest" and I was planning on doing it with "At My Most Beautiful" - R.E.M., when I was going to have a piano and violin duo). If not you need to get your songs onto a CD with notes for the technician who will be running the CD player.
There's also the option for an IPOD setup and having a friend or family member run that. In which case you need a playlist on your IPOD.
HTH!