HOMEMADE VINEGAR

Pour wine into a quart jar. Cover it with a clean cloth and tie it in place with a length of string to keep out any possible intruders; but remember you have to let it breathe to turn to vinegar.  Keep it at room temperature away from bright sunlight.  Wait.  Check it every few weeks or so and it will eventually do it's thing. 

You can use any wine but this is especially useful when you find yourself throwing away "old" wine or bits of bottles-it will still be perfectly good for making vinegar.  I have no qualms about mixing red and white if common sense dictates doing so.

Some wines have preservatives. They will still make vinegar but it will take a good while.  The older the vinegar gets the better the flavor.  The acidity will vary.

You may observe something cloudy which may eventually form something that looks like this: 

or this if it is white wine:

This is called "Mother of Vinegar".  In Italian and French country homes it is shared (if you're nice) or passed along from generation to generation.