Prepare your space. The spot you will be using to meditate should be free from distraction. This includes both auditory and visual distraction, so pick a quiet place that isn’t cluttered. Your meditation spot should be conducive to peaceful thoughts.
Position your body. Ideally, you should sit with your legs underneath you so that you are seated on the backs of your calves. This can also be accomplished with a pillow between your backside and your legs, or a specialized seat. The seat is in an “I” shape, where your backside sits on the top (usually curved to accomidate this part of the body, specifically) and the legs passing underneath the seat to either side of a central support beam. The bottom has another horizontal piece for support. The effect is that you appear to be sitting on your legs but are actually seated, and there is no pressure on your legs (facilitating better circulation).
Position your hands. This is, as far as I know, the only difference between men and women. For men, you place your left hand in your right; women place your right hand in your left. This is traditional, the reason for which is lost to antiquity. Place both hands in your lap, cupped as though holding a small bowl. The thumbs can either be joined in a steeple over the hands, or left alongside the hands.
Place the tip of your tongue on the roof of your mouth just behind the ridge of the mouth, where it meets the soft palette. This is supposed to create a connection for your internal energy to circulate. This is more common in the East Asia forms of Buddhism (Chinese and Zen) then in the more western Asiatic countries (Tibetan, Thai, India, etc.) Sit comfortably. Your back does not need to be stiff as a board, which is more a martial arts variation on meditation, meant to instill discipline. Your body should be relaxed,
in a position which will remain comfortable over a long period of time.
Concentrate your mind. The Principal of Right Concentration, a part of the Noble Eightfold Path, is probably the best guide to what proper concentration and meditation is. This is the Principal of Right Concentration, taken directly from Pali Cannon:And what is right concentration?Herein a monk aloof from sense desires, aloof from unwholesome thoughts, attains to and abides in the first meditative absorption [jhana], which is detachment-born and accompanied by applied thought, sustained thought, joy, and bliss.By allaying applied and sustained thought he attains to, and abides in the second jhana, which is inner tranquillity, which is unification (of the mind), devoid of applied and sustained thought, and which has joy and bliss.By detachment from joy he dwells in equanimity, mindful, and with clear comprehension and enjoys bliss in body, and attains to and abides in the third jhana, which the noble ones [ariyas]call “dwelling in equanimity, mindfulness, and bliss”.By giving up of bliss and suffering, by the disappearance already of joy and sorrow, he attains to, and abides in the fourth jhana, which is neither suffering nor bliss, and which is the purity of equanimity — mindfulness.This is called right concentration.