Tantra is not technique but prayer. Is not head oriented but a relaxation into the heart. Please remember it. Many books have been written on Tantra, they all talk about technique but the real Tantra has nothing to do with technique. The real Tantra cannot be written about, the real Tantra has to be imbibed.
If you move into sex with awareness, it can turn into tantra. If you move into tantra with unawareness, it can fall and become ordinary sex.