An exercise of controlling your attention. The three main general types of meditation are:
focused attention (concentrating your mind on a single point);
open monitoring (being aware of whatever is in your experience in the present moment);
pure awareness (resting the attention on consciousness, not distracted and not engaged).
Meditation is specially emphasized in the spiritual traditions that originated from India (Buddhism, Vedanta, Yoga, Tantra, Jainism, etc.), and those of the mystic side of the abrahamic religions (Sufi, Christian saints, Jewish mystics).
Present in all theistic paths, prayer is an exercise of directing our mind to the Divine, with devotion and surrender. It may be scripted or spontaneous; spoken out loud, silently in the mind, or without words (pure communion).
Breath & Energy Work.
These are specific ways of breathing and moving our attention through the body. They are often accompanied by visualization or repetition of sacred sounds (mantras). It can be done for the purpose of healing, energizing, purifying, calming, contemplating, etc. Examples are the pranayama from Yoga and the qigong from Daoism. It is also advised as a preparation exercise for meditation, which is more subtle and internal.
In conjunction to breath-work, some traditions use body postures and movements for developing health, freeing energy flow, and other purposes. Here we have the asanas of Yoga, Buddhist mudras, and several exercises from the Daoist tradition and Tantric schools.
Qualities of Mind/Heart.
All traditions speak of the development of certain qualities of mind and heart. Common virtues that are valued are: tranquility, equanimity, humility, detachment, loving-kindness, compassion, trust, devotion, discipline, courage, mindfulness, concentration, truthfulness, morality, discernment, and energy. These are developed through reflection, study, specific meditation and breathing techniques, and mainly by being mindful of them in our moment-after-moment choices.
Chanting is used in some paths as a means of prayer, study, and focusing of the mind in preparation for meditation. In devotional paths it is used for developing feelings of surrender and devotion; in other traditions, key texts are sometimes chanted instead of being read, as a help for memorization and contemplation.
Asceticism: Fasting, silent retreats etc.
Periods of intense self-discipline, simplicity, and no self-indulgence. These include fasting, intensive retreats, vows of silence, abstinence, long hours of meditation, etc. It’s like a “mind detox” or “spiritual cleansing”, and it’s a great way to burn negative patterns and quickly advance in the practice. It develops will power, self-control, and a sense of peace and contentment that depends on nothing else. In Yoga traditions they call this tapas.