Various methods for making marijuana oil or butter are covered in the Cooking Basics  section.
Another type of oil which is very potent is currently being used to cure cancer and for various other health issues. This is called Hemp Oil and the process to make it is involved but creates a very powerful substance. The recipe below was created by Rick Simpson.
More information about Hemp Oil can be found here .
THC is not soluble in water, therefore it is best to add either alcohol or fat to insure the THC dissolves into your tea. An ounce of whole milk or cream or a half ounce of liquor per cup of boiling water will increase the tea’s potency.
Chai tea  made with marijuana leaves, spices, butter and milk or cream dissolves more THC and makes a deliciously soothing beverage. Simmering the herbs for 15 to 20 minutes also helps to increase the THC content of the tea. Alternatively adding about 1 Tablespoon of marijuana butter  into your favourite tea is a quick tasty solution.
Making medicinal marijuana tea uses a fair amount of cannabis. Amounts should be varied according to your needs and the potency of the marijuana. Generally around 1 cup or 1 gram of herb can be used for 4 cups (1 litre) of water.
THC can also be administered via suppositories, through skin or under the tongue, although these methods aren’t commonly used. Cannabis seeds are also very nutritious with the optimum balance of Omega3 and Omega6 fatty acids as well as GLA (gamma-linolenic acid).