1. Open iTunes and plug in your iphone
2. Under the “info” tab you will see a field that “Sync Contacts with :” and give you a choice of which program you want to save your contacts to .By default, it is Windows Address Book.
3. Check the “Sync Contacts With:”box and choose windows Address Book
4. In the lower-right corner click the sync button and all of your contacts will be immediately saved to Windows Address Book
Next time when you want to sync these contacts to your new iphone, you just add them to itunes library, and I belive you know how to do the rest.
Here I find some interesting articles about

, maybe it will help you.