Fish them anytime and bang them off any cover.
You literally want the bait coming in contact with whatever your fishing like stumps, rip-rap, laydowns, grass, etc...
You picked a good starting point, the square A is a great lure and its cheap enough you don't have to be afraid to lose em'
Here's how I believe square bills work, http://www.bassresource.com/bass-fishing-forums/topic/143817-how-squarebills-work/