Medical Marijuana
Inhalation
Vapor is generated by heating or toasting the shredded cannabis flower (bud) and/or leaf into a colorless "smoke". Instruments (vaporizers) are made specifically for this purpose. They contain a heating coil that bring the plant to a specific temperature and vaporizes its oils. Less tar is produced and presumably less harm is caused to the lung and airways.
Steam is an older method, rarely used. Traditionally, ancient Greeks steamed the plant on hot rocks and inhaled the vapor under a tarp. An easy home method is to boil a pot of water and then emerge cannabis leaf and flower into the water creating a steam. A towel is placed over the head and the steam is inhaled. Eucalyptus leaves can also be added, making an excellent "old-fashioned" decongestant.