I try to take a tablespoon or two every day, usually in the morning when I get up and after dinner before bed. I think it's pretty hard to take too much of it though, today alone I've had about 6 spoonfulls and half a mug of tea with at least 3 tablespoons in it and am suffering no problems because of it.
You can take it straight in a spoon, kind of like taking a shot, or you can mix it with water or juice or something. It's not good for your teeth so I usually just pour the spoonful right down my throat. It burns a little bit for a minute or two, but that feeling leaves quickly and always seems to bring relief of whatever stomach ache (or anxiousness) I may have. If you do want to mix it you can put it in apple juice or in a glass of water with honey. I like it in a mug of hot water with lemon and honey too.
Bragg's seems to be the best kind because it's organic and unpasteurized and has the mother of vinegar in it, which is the stuff you'll see floating around (also why you want to shake it before taking) that is made up of probiotics which are great for digestion.