Syncing iPhone with one Mac but not another

iTunes includes a global option to not automatically sync when any iPod or iPhone is connected.

With iTunes on your Mac at work, go to iTunes > Preferences. Under the Devices tab, select prevent iPods and iPhones from syncing automatically.

If you deselect automatically sync when this iPhone is connected under the Summary tab for your iPhone sync preferences with iTunes, it won't automatically sync when your iPhone is connected to iTunes, which requires manually selecting Sync.

In the iTunes menu up top, find preferences and in one of the tabs (devices I think) is option to now have iTunes autosync anything. Turn that off at work. It is not the same as the checkbox (which effects settings for that device itself).

From the user guide, page 16, http://manuals.info.apple.com/enUS/iPhone_UserGuide.pdf

You may want to prevent iPhone from syncing automatically when you connect iPhone to a computer other than the one you usually sync with.

1. Turn off automatic syncing for iPhone: Connect iPhone to your computer. In iTunes, select iPhone in the sidebar, then click the Summary tab. Deselect “Automatically sync when this iPhone is connected.” You can always sync by clicking the Sync button.

2. Prevent automatic syncing for all iPhones and iPods: In iTunes choose iTunes > Preferences (on a Mac) or Edit > Preferences (on a PC), click Devices, and select “Disable automatic syncing for all iPhones and iPods. If this checkbox is selected, iPhone won’t sync automatically, even if “Automatically sync when this iPhone is connected” is selected in the Summary pane.

3. Prevent automatic syncing one time, without changing settings: Open iTunes. Then, as you connect iPhone to your computer, press and hold Command-Option (on a Mac) or Shift-Control (on a PC) until you see iPhone appear in the sidebar."

I use option 3 without any problems.