With the release of iOS 5 one of the best features they have added is that you no longer need to connect your device to your Mac when you want to synchronize your information. The Wi-Fi Sync works over a Wi-Fi network rather then through your USB cable connection. This syncing process works in the background and that means you can be on your device reading your emails and synchronizing your favourite album at the same time.

To enable Wi-Fi sync for your device, you need to connect your device to your computer, open iTunes. Click on your device in the source list (left hand side) and move down to the bottom of the summary pane.

Now you will need to checkmark "Sync With This Device" and "Open iTunes When This Phone Is Connected" and press the Sync button.
This will enable the Wi-Fi Sync.

By default, your device will sync with iTunes any time it’s plugged in and both are on the same Wi-Fi network however if you are sitting around on your couch without having it plugged in you can force a sync to happen by going into Settings on your device, General > iTunes Wi-Fi Sync and then tap Sync Now.

Enjoy!