iTunes Sync - Manually Control How do I control iTunes Sync to control exactly what I would like to upload to my iPhone or iPad?

Note: I am running iOS 5 on the phone, and iOS 6 on the iPad.
In iTunes go to the upper right hand corner:



select the device (iPad or iPhone), then this window opens:



Put a check mark in the box marked with red in the photo above (Sync only checked songs and videos).  You'll be able to select what Music/Videos are checked by selecting the Music or Movies tab at the top of this picture (notice Summary is currently selected).