How do I achieve orgasm without direct clitoral stimulation? 30% of women can do this, so how do I do this? Are there ways to increase my chances?

Try G-Spot. The g-spot is an area that arises out of the anterior (upper when you are laying on your back) wall of the vagina. Massaging this area while be stimulated sexually can cause the area to produce a small raised bump known as the g-spot. Continued massage of this area can lead to very strong orgasms even without clitoral stimulation.
Sensitive question. As with the male anatomy there are sensitive areas of the female anatomy that contribute to the orgasm sequence other than the glans or clitoris. The answer you are looking for may be in the article that said 30% of women can do it. Orgasm is much more that physical stimulating especially for women.