The Goetia is also called the Lesser Key of Solomon. While it contains several sections, the one that concerns us is the 72 spirits that are, wrongly, classified as demons. Many of them are simply gods or goddesses from religions that pre-date Christianity.
I do not use or teach the standard conjurations in the book. There are several reasons for this. One such reason is that to command these spirits to appear and do your bidding in the name of the Christian (or any other religion's) God is extremely disrespectful of these spirits, their offices, and the high station that befits them. Another reason I do not use the traditional conjurations is that they are not immediately useful and tend to lead to, at best, jumbled energy.
Instead, what I do, and recommend anyone that wishes to work with these spirits do, is look up the name of a spirit that can help you with what you seek in the Goetic Spirits Section of this website. Once you've found the one you wish to work with, chant his or her name several times, allowing yourself to become conscious of the spirit's energy. Once this is felt, either pray to the spirit for what you seek, or converse with the spirit about the matter, then ask him or her to do what you wish. You should never beg or plead, but you shouldn't be disrespectful either. Simply state what you need done. There is no need to license the spirit to depart. The spirit will depart, quite naturally, when communication is over.