I'm not going to lie: this isn't the best way to make tvorog. In fact, it can hardly be called tvorog at all because it's really more like a paneer or a farmer's cheese than tvorog -- it lacks the tang of a true tvorog. Still -- if you're in a hurry, or if you have a gallon of milk that's about to go bad, or if you like your soft cheeses to be milder and sweeter this is a perfectly good method. Traditional, proper tvorog depends on live cultures from kefir, cultured sour cream or buttermilk (or in the case of raw milk, you can culture it by simply letting it sit out and go sour). As demonstrated here, you mix warm milk with your culture and let it sit for a day. Heat again, separate the curds and there you have it.
This is faster, and while the flavors are decidedly less complex, it's still a good cheese.
You need:
Milk - 1/2 gallon
Vinegar - 1/4 cup