What is the BEST way to delete an app on an iPhone 4S so it will NOT be added back when I sync with iTunes?

To completely remove an app and all of its data, do this: First delete the app on your phone, then in iTunes, under Library, click on Apps, right-click the app you want to delete & select delete, when prompted, move all files to trash, empty your trash. Connect your phone and sync. The app and all of its data will be gone.

Delete it from iTunes too so it can't be synced back.