These sometimes involve specific reflections, contemplations, visualisations, breathing techniques, concentration on an object etc. The main point is to learn how to keep the mind where one wants it to be - in a place which is bringing much benefit to oneself and others. Buddhist practice, and meditation in particular, is often compared to a medicine. The patient is one's mind. Its ailments are all the unwanted pains of existence and limitations of mind.
Health is the fully-awakened, linitless mind of enlightenment.
A good teacher is like a good doctor. Just as a good doctor diagnoses each patient's case and prescribes a treatment just right for that person, so does a good Buddhist meditation master come to understand the unique mixture of elements that each one of us is composed of, and prescribe a series of meditations best suited to each individual's development. Thus the main thing to learn is a technique suited to one's aspirations, possibilities, strengths and weaknesses. This touches on the beauty of there being many ways within Buddhism, each responding to different needs. However, one can say that, in general, all Buddhist meditation involves working with body, speech and mind.