If you want to make your own mother culture, go to whole foods or any store that carries all natural raw unfiltered vinegar in the style you will be making (i.e. apple cider, red wine, white wine etc...). They all have a slightly different culture in them, so don't use an apple cider culture to make red wine vinegar. Check them bottom of the bottle, you will likely see a sediment, or if you're lucky, you will see a slimy whittish glob in the bottle. you can add a few tablespoons of this to your wine in a crock, jar or bucket. Leave open, but place a tea towel or cheese cloth over t and secure with string or rubber band (this will keep the flies out). Leave it to sit for a few weeks to a month, then taste. You should start getting your conversion by then, but you will want to let it go for a couple more weeks or months depending on how sour you want it. When it is done, the mother should look like a disc of slime, remove it and collect your vinegar. You can break the mother up and add to more wine to get started again if you want.
I usually dump all my leftover wine into a crock I keep a perpetual batch of vinegar going in. Once you have a good mother, you will have good, reliable and very tasty vinegar. Keep a seperate container for each type, red, white, apple etc...
Dos Locos is right, keep the vinegar in a pantry, cupboard or storage area where none of your brewing equipment is located. I keep mine in my pantry, and have never had a proble with cross contamination, just make sure your sanitary proceedures are strong when you are brewing.