To make vinegar you need a crock, mother of vinegar and wine.
Christmas is a good time to start making vinegar because you'll probably have left over wine, or your friends will. Instead of throwing it out, or leaving it to sour in the fridge or cupboard, why not make some vinegar!
First you'll have to go looking for mother. No, not your mother, mother of vinegar. That is what the slimy disc of bacteria is called that sometimes forms on store bought vinegar. Pick up the bottles in the store and look to see if there's a floating disc of slime on the top. Strange but true, this is what you want! I first found mother of vinegar in a bottle of unpasteurized apple cider vinegar I bought at my local IGA. I thought the mother had formed because the vinegar was unpasteurised but since then I've had mother form in the cheaper vinegar I bought at a supermarket. Both of these are fine for making vinegar.
You'll need a glass or pottery crock. I use the crock I used make my ginger beer in. I have a bigger crock for the ginger beer now. It has a little spigot that allows me to easily syphon off the vinegar. You'll also need a cotton or linen cloth to cover the crock so bugs and vinegar flies don't get in. You need air to enter but you don't want it to become contaminated with anything else.
The only other thing you'll need is wine - this can be any quality. If you want red wine vinegar, you use red wine, or white wine if you want white wine vinegar. Don't mix the two. I'm making white wine vinegar.
Just add the mother of vinegar to some wine. If you have a full bottle, pour the lot in, if not, start with a glass or two and add more wine as it becomes available. That's why I said Christmas is a good time to make vinegar - you can ask your friends to save any left over wine they have at parties. It's okay to add different kinds of white wine to the one bottle, ditto with the red wine, but don't mix red and white white together.
Like sourdough starter, home made vinegar improves with age. You don't empty the crock, you always keep some of the old mix to blend with the new additions of wine. Your matured vinegar will infuse the new wine with its flavour. Each time you make vinegar with some of your old vinegar added, it will have a greater depth of flavour.
The best way to tell if your vinegar is ready is to taste it. It will probably take between two and four months to mature, if the temp in your home is around 25 - 30 C degrees (around 80F). It will take more time in colder temperatures.
Very good information about vinegar
The virtues of homemade vinegar
Types of vinegar