Taste the grapes. I assume they are a concord or catawba grape variety if they are "yard grapes". If they are not wine grapes, they will be tasty but tart and acidic and low in sugar.
I use 6 pounds per gallon of grapes, and enough sugar to boost the OG to 1.095 or so. You have to add water, also, to dilute the acidity.
I don't have a press, so I freeze the grapes (seeds and all, but destemmed) in big garbage bags. When I go to make the wine, I put the grapes in big mesh bags and put them in a sanitized primary. I add some boiling water and add one campden tablet per gallon. I then check the SG and add sugar /water to bring up the OG and the volume. (Some easy math helps with this).
I add a bit of powdered tannin, some yeast nutrient, and any other needed items (I doubt you'll need acid blend). Wait 12 hours, and then add pectic enzyme. Wait 12 more hours, then pitch the yeast. Cover with a thick towel to keep out fruitflies!
Stir twice a day for about 5 days. Smash up the grapes with a mash paddle or heavy stainless spoon. Since the grapes were frozen, it's easier for them to break up (no stomping required!) Make sure you stir down the "cap" that forms so the grapes don't dry out. Then, remove the bags of fruit and squeeze them as much as you can to get out every bit of juice. I take them into a new sanitized bucket and press down thoroughly.
Then, transfer to carboys, and airlock. Top up when fermentation slows.
That recipe works for catawba grapes and concord grapes. I don't know much about other grapes like muscadines.
I love Jack Keller's site and here's the part on native grapes:
http://winemaking.jackkeller.net/nativew1.asp
Scroll down a bit and he tells how to drop the acidity if necessary for some very tangy grapes.
