The Guru (teacher or master) in ancient Tantric traditions and lineages played an important role. Moreover, it was generally thought that nobody could engage on the Tantric path and study Tantric techniques without the acceptance, help, and initiation of a Guru.
Today, Tantra has become somewhat more “something of the public” and with that also the role the modern Guru plays. Although there are certainly still extraordinary Gurus to be found — the real sages and adepts — the majority of teachings today is given by more ordinary Tantric teachers, not necessarily adepts, sages, saints, or spiritually enlightened beings.
That, of course, doesn’t mean that a modern Tantra teacher shouldn’t have specific qualities. There are a few guidelines here to be taken into consideration. For instance, a Tantra teacher should have had adequate training and master the topics they teach, should be a psychologically “stable” person, should have moral self-control, have more knowledge than their student in the subject taught, have didactic skills, and have compassion and patience, among others.
Specifically in Tantric Sex practices it goes almost without saying that clearness, consent, and trust are of crucial importance. Any form of sexual abuse or a feeling thereof should be avoided, and the teacher should be very explicit and clear about the way they work and what can be expected of a training course.