There are many types of meditation that can benefit you in many ways. The meditation that I will be covering is a Taoist method. The reason I will be covering this method is because it goes hand in hand with the Martial Arts that we practice, and it is the oldest form in China. Technically, Qigong, Tai Chi, Bagua, and Xing-Yi are forms of meditation because the breathing and torso methods follow the exact principals of Chinese Indigineous meditation. This is what separates them from the woody, rigid, external martial arts.
   There is a saying in Internal Martial Arts: "The soft is associated with the living, and the hard is associated with the dead." This saying is true because when you look at a tree for instance, the branches are flexible when they are healthy and stiff/brittle when the tree is dead. As you can see it is easy to break something that is hard, and the soft will give way.
   When one imagines meditation, they tend to think of Bhuddist monks sitting and meditating. Bhuddist meditation is very similar to Taoism. In fact, in the Hua Hu Jing (A mostly unknown writing of Lao Tzu) it mentions that Chan Bhuddism (Also known as Mahayana) actually has roots in Taoism. This is also evident due to the fact that Ta Mo (An Enlightened Indian Bhuddist Monk also known a Bodhidharma, who is credited as the creator of Shaolin Lohan Martial Arts) taught the monks of Shaolin some breathing and torso methods to keep them from falling asleep during meditation. He did this by combining Indian Yoga postures with the Chinese native qigong called Daoyin/Tuna (A form of qigong that imitated animals practiced in China for thousands of years earlier). This is where the first Shaolin Qigong is said to have started, and what eventually evolved into the first Shaolin Martial Arts system.

   The only major difference between the two methods is the fact that Bhuddist focus on returning to one's original nature (mind), but ignores the phenomenons that happen within the body during the different stages. The Taoist method cultivates the mind and pays careful attention to the different reactions in the body. (i.e. Reactions in the head due to the opening of the Tu Mai or Governing Channel, or the sexual effects because of the opening of the Jen Mai/Conception Channel, etc.)
   One thing that all meditation methods have in common is the goal of cultivation of Dao. With consultation of an experienced teacher and practice over time, one will feel more relaxed and can avoid going down the wrong path. It is reccomended that one practice Tai Chi or an internal exercise after this meditation in order to avoid the reactions one may experience due to lack of guidance.  If one has a latent illness or disease, it will show it's self; and one should stop meditation and seek treatment immediately. Although you should see a doctor, you can meditate with the intention of beating the illness once you are taking the medication. This could help with the recovery of one's health. It may be caused by an imbalance, and meditation/qigong is only trying to fix that imbalance. As far as reactions in the head, one may also begin to hallucinate or see demonic images. This is because of the opening of the Chi routes (Meridians) in the head and the stimulation of subconscious thoughts or religious beliefs. Please remember that these illnesses or mental reactions are NOT caused by meditation, so one should treat these illnesses before trying to meditate again. And if one see's strange images, they should ignore these images and get past them. These are only caused by one's mind, but without proper guidance one may not be able to pass this stage. I am not responsible for such reactions, and therefore advise that if you are going to attempt to meditate without guidance, you should meditate at your own risk.