To add to this, If you are going to use the bugs that live on the cider, Patience is Paramount.
I had a gallon of local cider start fermenting on its own, and so I let it sit (with the cap loosened) to allow it to ferment. The first 2-3 months may have been some of the worst sulfur smells I have ever smelled, but after about 3-6 months, the sulfur blew off, and left a great complex apple/lactic flavor, with a touch of barnyard. It turned into a great cider that was very tasty, and incredibly deep in flavor, despite being completely dry (.998).
If you are going to do what Mort recommends, take a gallon of cider, pour out about 1 1/2 cups, and put the lid back on softly, cover with foil, or add an airlock. I wouldn't do more than a gallon until you know you like it.