From someone who has passed over 300 stones (I quit counting at 300 approx 5 years ago - Passed by first stone 11 years ago) - I found that mine were caused by a lack of potassium - I started eating several bananas a week, and a few potassium supplement pills (although they claim to be only 3% of your daily value per serving/pill on most over the counter bottles) - I haven't had a kidney stone in 6 months or so, been eating the 'naners and popping the potassium for around 9 months give or take.. I had tried other things in the past like taking coral calcium (for some people a lack of calcium can actually cause you to produce more stones, weirdly enough (most stones are made up of calcium oxalate)).
<Edit> I've heard the citric acid thing, but from what I've been told by numerous doctors, that is just a myth.. Water, though, is a key element in getting the things to pass quicker, as well as beer, but the beer can cause more problems by dehydrating you, however, while passing stones, a few beers isn't a bad idea though, because it will help em pass faster.. Just drink in moderation..</edit>
<Edit> I've heard the citric acid thing, but from what I've been told by numerous doctors, that is just a myth.. Water, though, is a key element in getting the things to pass quicker, as well as beer, but the beer can cause more problems by dehydrating you, however, while passing stones, a few beers isn't a bad idea though, because it will help em pass faster.. Just drink in moderation..</edit>
