This is an interesting question. I have spoken with many experts in probiotics over the years, Dr. Khem Shahani and Dr. Dash were two pioneers in the probiotic field in America, and they have taught me many concepts about probiotics which have changed the way I work with them. But my own experiences with patients in the clinic have taught me a lot more. To begin with, you should try and get into your mind that "take one capsule with meals once or twice a day or as directed by your physician" is purely only a guideline. Probiotics DO work, and they can work very well if you learn a little more about them. Same goes with any other dietary supplement though. For example, when you take Vitamin D (fat soluble) you are best to take it with a meal containing fat. I am starting to learn that probiotics work best when given with specific enzymes, because in nature, most raw foods which contain beneficials also contain enzymes. Nature is not stupid, she knows what is best. Probiotics also work the best when you eat foods conducive to their growth and survival. They are not "magic pills" that "put lots of good bacteria in your bowels" as many folks think they do, they are extremely sensitive micro-organisms which are easily influenced by the mileau of your gut, and can thrive or die very easily depending on how you take them, how they were stored, what you take them with.
I have experimented with candida patients and probiotics for many years, and to be totally honest, I find good old Lactobacillus acidophilus (in sufficient dosages) to help most folks.
But here's the kicker - step up your intake of lactic acid, lactobacillus loves a lactic rich environment in your gut, supplements like whey are a super food for lactobacillus species and can sky rocket the health of your gut. Eat kefir, yogurt, sauerkraut, tempeh, kim chi, natto, miso, etc, etc. Read Sally Fallon's Nourishing Traditions book which contains a wealth of information about this. Taking probiotics AND eating these foods does the trick. Trying to eat a high protein diet, lots of vegetables, coconut products, paleo, GAPS, whatever - it is not enough if you just can't seem to beat that beast called yeast. You have to "cultivate to eradicate", my Candida Crusher book explains this approach in great detail, I have devoted over 200 pages in my 712 page book just about diet and nutrition.
Try to cultivate your gut like a garden, you tend to get rid of the weeds (yeasts & bacteria, parasites, etc) more so by feeding up the lawn, rather than by spraying the weeds and focusing on that "kill" approach that everybody seems to do. The healthier the grass, the less chance weeds can take a foot hold.