Q. Please ask your readers if they know how to make apple cider vinegar at home.
A. Look for a bottle of apple cider vinegar that hasn't been processed heavily, and/or for one with a layer of brown sediment at the bottom. This is the "mother", and, if it hasn't been pasteurized, which will kill it, is the bacteria for making vinegar. If you are working with your own pressed juice, there will be bacteria from the environment in it, which may or may not be the type you want. You may want to pasteurize (and then cool) the juice before putting some of the "mother" in it. From here, I would proceed as if making wine, with an air lock on the bottle to prevent other, unwanted, bacteria from getting in. You may be able to just let the juice work on its own, but the risk of spoilage is higher. Once you have a good batch of vinegar, be sure to keep a sample of it to inoculate future batches - just like sour-dough. You might experiment with freezing small quantities - like in an ice cube tray - so you always have a ready supply.