With the lack of a 3-keto group, and the addition of a pentangle at the 2 and 3 positions, one could liken the structure of Danazol best to Stanozolol (Winstrol/Stromba) or Furazabol (Miotolan). But for proper understanding of this drug its best likened to Mesterolone (proviron). Its similar, but a lot less androgenic. Like mesterolone it's a steroid, but rarely regarded as such. Because of its structure its only mildly androgenic and because it binds readily in a lot of places in the body without exerting any real action, its not considered anabolic to any degree. So you can derive that the use of danazol is not that of the classic anabolic, androgenic steroid. In treatment Danazol is used as an anti-gonadotropin. Its exogenous administration gives negative feedback to the natural production of testosterone, slowing it down, but mostly it's a competitive anti-aromatase. And for that reason its sometimes employed by bodybuilders to prevent the side-effects of aromatization of certain hormones like testosterone. These side-effects include bloating through water retention, increased body-fat and gyno (growth of breast tissue in men).
I do say "sometimes" because Danazol is hard to come by these days, as is illustrated by the large number of products in the product list above that have been discontinued. On the black market too it seems the interest in this compound is relatively low, and prices considerably high. As high as 350 dollars for 100 tabs of 200 mg, and knowing the daily dose is easily 400 mg per day, that's a costly affair. That's why you won't hear much of danazol in popular literature. But in the scientific literature its still frequently used for research purposes.
Possible side-effects that can occur with use are of course very mild. Like Proviron it does not aromatize to any extent and actually prevents aromatization, and the lack of a 3-keto group amongst other things makes it a particularly poor androgen, so androgenic risk is limited. One might still note increased libido and some acne however. Perspiration, hot flashes, elevated blood pressure and liver toxicity (to a small extent, due to the high doses) can be encountered if using very high doses for extended periods of time.
Danazol may make a great alternative for Proviron, but with Proviron, arimidex, cytadren and several others available to us, the need for another mild, expensive aromatase inhibitor is limited, hence its low presence on the black market. Many governments and sports federations have also banned Danazol because of its slight androgenic effect, making things like Arimidex a much more popular choice, and selling for roughly the same on average, and those who are tied in, even a lot cheaper due to the wide-spread availability of anastrozole (Arimidex) to the underground manufacturers.
Ideally one would stack Danazol with aromatizing steroids like nandrolone, testosterone, methandrostenolone and boldenone to limit or stop them from aromatizing, and thus eliminating or reducing estrogenic side-effects. Since its an aromatase inhibitor, it would most likely be employed for continuous use. If it was merely as a short term problem-solving measure an estrogen receptor antagonist like Clomid or Nolvadex may be handier. For these purposes a dose of 200-400 mg daily is employed. The higher end being the more common. It needs to be noted that there is a downside to blocking estrogen formation as well, because estrogen increases our gains. It is (as demonstrated in the Equipoise profile) helpful in upgrading the androgen receptor, increasing natural growth hormone output and improving glucose utilization for extra energy and a sense of well-being. These are things a user needs to be aware of. Obviously a little water retention is not a big deal or you would not have chosen an aromatizing compound to begin with, so unless you are particularly sensitive to estrogenic side-effects, keeping an estrogen receptor antagonist (Nolvadex or Clomid) handy, just in case, instead of running an aromatase inhibitor throughout, will allow you to get more mass out of a cycle.
Since Danazol is an anti-gonadotropin, the post-cycle use of Clomid or Nolvadex is required, maybe even in conjunction with a preceding HCG therapy to bring natural testosterone back, but since one would only really opt for Danazol in conjunction with suppressive aromatizing steroids, you would already be doing this anyway if you know what is good for you, so surely I'm just mentioning this for no reason (although one can never be too safe). There is no real use for other ancillaries with this compound.