In iTunes, go to Edit > Preferences > Devices. Once there, you'll see a box titled something like "prevent iDevices from syncing automatically.". Make sure that box is checked.
Oh, and I also Make sure iTunes doesn't automatically check for firmware updates (which is under Edit > Preferences > General; untick the box). That may just be the rebel in me, but I like to make my own decisions as to what stuff is done when...
I also like to ensure iTunes doesn't open when I plug my device in (I'll control the behavior, thank you!). So, when the iPad is plugged in - on the Summary tab, at the bottom, I also ensure the box that reads "Open iTunes when this iPad is connected" is unchecked.
Then, with the iPad still plugged in, under the Apps tab, I make sure the box under the apps list (titled "Automatically sync new apps" is also unchecked...
Hope some of this helps.
Marilyn