Meditation is a generic word for different kind of techniques to stop the fluctuations of the mind. Meditation in Ashtanga Yoga has the sanskrit name Dhyana which is a specific state of awareness. It's not any kind of effort to silent the mind, but the silent mind. It is the result of other yoga practices which purify the mind, the emotions and the body.
In my classes, workshops and retreats, I sometimes do preparatory exercises for the meditation. First stage is to be able to sit still. No movement in the body, just the awareness of one's own mind. Next stage is Dharana, which means one-pointed mind. There are different ways to practice this, like mantras, Trataka (gazing a flame or some other external object). When the mind can stay for a long time in the Dharana state, it naturally starts to evolve towards Dhyana, meditation. The Dhyana state can't be reached if one's life is full of distraction or stress. The life style needs to support the mental-emotional and spiritual process. To sit silently daily requires discpline that can come through a devoted asana practice. Beginners can start with a daily five minutes sitting.
In my retreat programs I sometimes have Osho meditations: Dynamic, Kundalini, Mandala or Gourishankar. These are all active meditations where the practitioner moves first the energy fiercely to get in contact with it and to liberate the mind, the emotions and the body totally. The meditator becomes the movement, the energy. I guide these meditations only with regular Ashtanga practitioners, because they require an understanding of and connection to the emotional body. For some people yoga practice can become just a method to control life energy and the problems. In Osho meditators I've witnessed great liberations in energy and emotions. I've met really open-hearted people who are connected to themselves, to others, to the whole Universe. I find this an excellent combination, to have a regular Ashtanga yoga practice and then once in a while take an "Osho cure" to explode what's stuck, give your energy freshness and life and share the deepest feelings with others.