When you plug in a new phone it will ask you if you want to restore it from an old backup. Just say no to taht. Once it is connected, you can rename it the same as you would change a folder. I gave my iPhone3 to a nephew and didn't have any problems having them both synced. That applies to a Mac. If you have a PC, you have to have a separate user account for every separate iPhone.
In iTunes, turn off automatic syncing to prevent thew old iPhone from syncing when you connect it to iTunes:
Preferences > Devices > Prevent iPods, iPhones and iPads from syncing automatically.
Connect the old iPhone. When it appears in thedevice list at the left of the iTunes window, click it's name to hilight it, then enter a new name. Sync the phone to update the name on the phone.
Turn automatic syncing back on if you want to. I prefer to leave it disabled, but that's up to you.
The easiest way to handle it is you each will have your own computer login with your own iTunes library. Then there is nothing to get mixed up.
I have my I tunes account which currently has my iphone named MyIPhone that syncs with it. It is an iPhone 4 and now I want to give my old Iphone 3G to my son and sync that to my Itunes account but that phone is named MyIphone as well so when I plugged that phone into I tunes I had to stop the sync as I want to wipe all of my stuff off the 3G before I make my son use. There is a new sim card inside but I need to know how to rename that phone so when I go to sync I do not sync my IPhone 4 apps email accounte etc. to that, follow?RD
The name of the iPhone has nothing to do with it.
Select the iPhone in iTunes, click the tabs across the top and select what you/he wants to sync.
To wipe it it first, select the iPhone in iTunes, click the Summary page and select Restore.
I recommend you each have your own computer login (even if you do not have iTunes/iPhones).
All your info is yours and his is his and you don't have to worry about having anything changed/deleted.