Bestop makes stuff to keep their tops clean: Bestop Soft Top Cleaner and Protectant - Quadratec
I use Aerospace 303 on my soft top (I've got an ORH top, but used it on my OEM top before I replaced it). I just spray the 303 on and scrub it in with a soft bristle brush. It'll get mud out of the nooks and crannies, too. You can get it at most marine supply stores, some hardware stores, or on Amazon. Keeps the fenders nice and black, too.
Some folks use Simple Green the same way as above.
Keep the zippers lubricated, as well. I live in a cold weather climate and the salt they use on the roads in winter can trash the zipper teeth in nothing flat.