Method 1: Keyboard Controls
Now, the easiest way to stop your iPod from syncing with iTunes is to open iTunes, and then hold down the Command + Option keys on a Mac or the Control + Alt keys on a PC. This will stop the two from syncing. You will have to hold down these keys for several seconds, generally between 3 and 25 seconds.
When you’re positive that your iPod has been recognized, but the iTunes hasn’t started syncing it, you can release the buttons. Then, you can go into the Edit tab, and the go to Preferences. In this menu, click on the Device tab. Click on the checkbox next to “Prevent iPods, iPhones, and iPads from syncing automatically". Then, press OK.
These instructions are for later versions of iTunes. If you have an earlier version, you should click on the iPod icon within the iTunes source column, and then select iPod Options. Click on the checkbox next to “Manually manage songs and playlists".
Both of these options will allow you to sync your iPod only when you are ready.