The first thing is that the practice of Tantra is not a way to have more or better orgasms. Somehow, we in the West are confused about what Tantra is about. We have misunderstood that it is about sexual positions, orgasm and techniques for longer lasting sex.
Tantra is a path for developing awareness, sensitivity and presence in all aspects of life. And since it is distinctly oriented toward developing consciousness through the everyday acts of living, including sex, it is a philosophy that is well-suited for passionate people. What Tantra cannot do is help you to achieve an orgasm. What Tantra can do is offer you a way of being relaxed, centered, empowered, present and capable of surrendering in the moment to whatever it is you are engaged in. In lovemaking, those elements produce the conditions in which orgasm occurs.
In other words, learn to relax, breathe, be present, be aware of your energy, your emotions, what you might fear that can create a tightening up on the physical level and prevent letting go into orgasm. Self-pleasuring is important for women who want to become more orgasmic. Betty Dodson has a very good video available. The one thing I would add is that once you are orgasmic with a vibrator you should get yourself a G-spot stimulator. Tantra.com sells one that is good. If you are in the San Francisco bay area, I teach courses on women's sexuality.