Or try this (or something like it)
When you connect a device to the new iTunes the first time, click the Devices button on the upper right in the Library view, select the device and check "Sync with this <device> over Wi-Fi" in the Options section. The device will now remain in the list even when it's not directly connected and it will sync automatically when it's on the same Wi-Fi network as your computer and you plug it into a power source. To change what you want synced, select the device and use the menu items across the top -- Summary, Info, Apps, and so on -- to choose what you want to have happen for that particular device for each category. (The Apps section in particular gives you a much cleaner, clearer way to manage your apps on different devices.) When you're done, click the Apply button on the bottom right to have your changes take effect the next time you sync.
http://www.apple.com/itunes/inside-i...ew-itunes.html