If you're like me and too clumsy to longline or spider rig or handle treblehooks: I park it right over the fish and tie on a heavy jighead (~1/4 oz.) with a good skirt (whatever I think is the right size and color for the conditions) and drop it to the bottom, right down the middle of whatever cover them pomoxii are holding onto. I use a good sensitive rod so I can feel the bait hit bottom, and if I'm not sure I yo-yo it a bit to feel the jig bouncing on bottom. Then I retreive vertically real real real real real real real slow and repeat until I get a bite. If I make 3-4 retrievals without a bite, I'll try another skirt (another size or color or style may be needed). If the fish are down there they will eventually bite, it's just a matter of presentation.
But I DO NOT reel in right away on the initial bite, first I make a mark on my line (with a sharpie) where it meets the rod tip. Hopefully I've found the 'magic' depth and will want to be able to easily drop right back down to that depth. Otherwise, I may get impatient and decide on subsequent drops that, even with a 1/4 oz. head, I'm spending way too much time waiting for the bait to fall when actually it's not reaching the fish at all...
That's my best method for success on deep water crappie.