text messages and voice messages are linked to your phone number and will transfer over automatically....although since the start of iMessage, not sure how that transfers over...sorry...but i would do a backup of your old phone before you activate your new phone, then when you get your new phone just do a restore from the latest back up and you'll have everything on your phone that you had before....
Hopefully i'm reading into your title correctly....are you getting a new phone or clearing out your old phone and starting over? My assumtion was that you are getting a new phone....
Sorry if it doesn't help....