plant the whole pit

Some people break open the pit because it makes the seed grow faster, but I just put the whole thing in a wet paper towel in a baggie and waited a week or so until it broke the pit itself and started sending out roots. Then I planted it outside. I've never planted grapes, but I'd imagine you'd have better luck in spring than winter; if you have a lot you could plant some now and plant some later and see what works best.
Good luck!