See page 7ff in the userguide:
http://manuals.info.apple.com/en_US/iPhone_User_Guide.pdfContacts, calendars, and webpage bookmarks are synced with applications on your
computer, as described in the following section. Contacts and calendars are synced
both ways between your computer and iPhone. New entries or changes you make
on iPhone are synced to your computer, and vice versa....
Disable automatic sync in itunes, connect your phone go to the Info Pane. Set up at least one contact and event on your mac, so youll have the option to merge your contacts and calendar when you sync them for the first time. Make sure to backup your phone manually before.
The Info pane lets you configure the sync settings for your contacts, calendars, email
accounts, and web browser.
Contacts
You can sync contacts with applications such as Mac OS X Address Book, Microsoft
Entourage, Yahoo! Address Book, and Google Address Book on a Mac, or with Yahoo!
Address Book, Google Address Book, Windows Address Book (Outlook Express),
Vista Contacts, or Microsoft Outlook 2003 or 2007 on a PC. (On a Mac, you can sync
contacts with multiple applications. On a PC, you can sync contacts with only one
application at a time.)
If you sync with Yahoo! Address Book, you only need to click Configure to enter your
new login information when you change your Yahoo! ID or password after you’ve
set up syncing...userguide, page 10ff
Message was edited by: Ingo2711
MBP 17 2,16GHz Mac OS X (10.5.7) iMac 2,4Ghz, ipod 5G, iPhone3G, ipod touch 2ndGen