The ability to do point meditation on the perineum (the point between one's genital and anus) is an essential step or hurdle to overcome in a practitioner's route to doing deep meditation. But how to do it? Many beginning meditators can't do it after the first few lessons. They are adamant. They talked to their teacher: I want to do it now, today!
In our age of consumerism, some teachers go along and tell them: If you can't focus on your perineum, squeeze your anus instead! Everybody immediately understands, probably because most have been in long-haul coach without toilet. So everybody excitedly squeeze their anus and do meditation. A teacher may figure that, well, he will move on to his perineum some day, but most never did.
A better way will be to learn from the yogis. I'm referring to the techniques of Mudras and Bandhas. Despite the complex theories behind, they are simply locks executed through subtle muscle contraction with holding of breath to magnify the effect. Whereas classical Taoist meditation frowns upon the holding of breath, I believe the use of which can be beneficial for beginning practitioners, with one caveat: watch out for one's heart conditions before doing lengthy breath holding.
Needless to say, the ability to focus on one's perineum is just a preparatory step towards deep meditation proper. The next step is to transfer the (mind's) control point from the perineum to the Dantian at the lower abdomen. Of course, that will be another story, stay tuned.