How do I prevent iTunes from syncing 400 apps to my new iPad? I just got my new iPad and installed the apps I wanted without first syncing it with my computer. When I connect it to my computer and choose to sync apps, iTunes wants to add all my 400+ purchased iPad apps to the iPad, and I don't want that. 

Is there an easy way to deselect these 400 apps that I don't want from within iTunes? They are arranged on the last screens after the apps that I actually want.
Unfortunately iTunes doesn't support selecting multiple applications, apart from manually selecting each one. The best option would be to disable syncing of Applications on iTunes.

For iTunes sync to work correctly you either need to use it to manage your applications, or only use the iPad and download all the applications you want directly to the iPad using the App Store on the iPad.