Ive got this all from reading, never done it before, and I havent read anywhere how much to take. If you can get higher percentage alcohol, like Everclear, use that instead.
Green Dragon is prepared by soaking cannabis in a high percentage spirit (brands such as Everclear 95% (available in the US) or Alcool 94% (available in Quebec, Canada at SAQ) are known to be most effective). The active chemical in cannabis (THC) is soluble in ethanol, and is leached from the cannabis into the alcohol.

The solution is generally left standing for several weeks before a significant amount of THC is absorbed by the alcohol. The leaching process, and the corresponding absorption process, are slow and ongoing, and the rate of reaction may be accelerated by heating the solution. The leaching process also changes the color of the solution (Everclear and Alcool are clear and colorless) to green, hence the name Green Dragon.

A decision must be made as to whether to leave the cannabis in or to separate it from the solution. By leaving the cannabis in the bottle the leaching reaction will continue while the bottle is consumed making the solution more potent as time passes. Removing the leaves from bottle produces a nicer looking solution.

Internet message boards recommend for best results minimum 14 grams (1/2 ounce) of cannabis per 750 mL (26 fluid ounces) of spirits (the required volume of cannabis varies with cannabis potency and desired strength for the green dragon beverage).

It is worth noting that green dragon must be stored in an air-sealable container to prevent evaporation and must be kept out of direct sun light to prevent the breakdown of the THC. Other typical strength alcohols (40% alcohol by volume) such as vodka or rum may be used in place of Everclear; however, a higher percentage alcohol solution is much more effective at extracting active chemicals from cannabis.

^^^ got that from Wiki