syncing iphone and itunes on same computer?

i just got the 4S and i want to give my daughter my old iphone3g as an itouch. how do i sync both these things on my one itunes, so that her apps/music/etc. and my apps/music/etc. stay separate? i'm afraid to experiment in case i wind up erasing my phone, so appreciate any suggestions.

i can only think of the manual way.

for example, you sync the 4S automatically and the 3G manually, with allows you to control the songs/movies etc..to your daughters phone. effectively creating a 3G playlist of music ...

sorry, doesn't seem much help reading it back, but it is all i have.

J

This should help you out should it not?

How to use multiple iPods, iPads, or iPhones with one computer

The best way is to have your computer set up so that you and your daughter log into separate computer accounts. The syncing process will only sync with the account your are logged into on your computer, not any other accounts there.

Apple tell you how to create accounts at Mac OS X 10.6 Help: Creating a new user account

btw it's a good idea for reasons of security that people create a "user" account on their computer rather than log in as the default account that came with your computer and has too many privileges to be used for day-to-day stuff. You and your daughter can use two separate user accounts and leave the admin account alone (while remembering its password for genuine software updates).