Check the picture of the tongue is one of the very important TCM diagnosis method. The tongue has many relationships and connections in the body, both to the meridians and the internal organs. In general, red tongue with yellow coating means heat in your body, pale tongue with white coating means cold or Qi and blood deficiency, thick slippery coating or greasy coating means water retention or dampness in your body. Different conditions needs different acupuncture points combination to treat.
Watch this video from Youtube to get more information about the tongue diagnosis.