This is what works for me on a Tab2 7, wi-fi model.
Go to settings/storage.
scroll down to 'cached data', select it and then select 'clear cache'.
Observe the colour bands depicting memory allocation.
Select Apps, delete any unwanted apps but be careful to not delete the basic set, if this folder doesn't take up much room, just leave it.
Scroll further down to see if there's a folder called 'misc' or similar, enter it. Mine was over 2g so I selected 2 huge folders in there and deleted them leaving some very small [8kb] folders alone for now.
The bar at the top shows how much you have recovered, I gained 3.5gb.
I rebooted just to be sure, all seems well. YMMV as they say.
Cheers,
Mac