To begin this operation, you need to bring to bear all your gimmicks. You need all your magical weapons, all you symbol systems, an act of power, and, ideally a symbolically significant time (dawn is good, dawn on your birthday is better, dawn on your birthday on a numerologically significant year is quite excellent. You can also select the day through astrology, numerology, or some combination thereof). You want to make your entire area as perfect a representation of the semiotic web, i.e. the cosmos, as you can. You may have to redecorate an entire room for this operation. Take your time. Make it perfect. You should also have some paper and a consecrated pen handy. You'll want to record what comes through, if anything.
First, banish the area. Stand at your place of working—altar or otherwise—and attain a state of deep relaxation and self-confidence. You may use an anchor for this, but take your time. You want as deep a state as you can possibly muster. Nothing should be halfway. You're reaching out for something very large here. If you have a tool dedicated to invocation, pick it up. You're going to try to invoke the HGA.
The problem is, of course, that you have no idea what the qualities of the HGA are! You don't even know its name! This is the hardest invocation you'll ever perform, because you'll need to rely on the invoked entity to come halfway. Fortunately, the HGA wants to communicate with you, once it knows you're willing. So you have to start to convince it that you're willing.
The best way to do this, while at the same time increasing your magical authority, is to begin reciting your accomplishments, no matter how large or small, including every act of power you've ever performed, every spell, every mundane success. You may feel silly recounting how you heroically recovered from the flu, but just keep pushing on. Don't think about what you're saying. Don't analyze, just recite.
At some point in this litany, which may take some time, you'll begin to feel something strange. You might start twitching or speaking in tongues. Maybe you'll just feel oddly diffuse in some intangible sense. Whatever happens, let your imagination take in every symbol of power with which you've surrounded yourself; let them congeal into an image, and let that image speak a word. That word is the HGA's name. Repeat the name aloud and write it down. You may also receive a sigil. If so, write that down, too. If you feel up to it, ask a question. "Where can I look for greater power?" might be a good initial question, as is, "How can I be a better person?" Record the answer, even if it makes no immediate sense.
Thank the image, giving it the license to depart as you would in an evocation. Then banish the area and—if you find the experience as draining as I do—collapse for a while. When you've recovered, try to see if the name, image, and answer to your question (if you have one) fit together symbolically. You may find the name means something in another language, or you may find some other connection. Remember, everything is a symbol like in a dream, and in a dream you won’t have any symbol you can't interpret. I can't give any more precise instructions than that. Here I have to leave the work up to you and your HGA.
From Postmodern Magic, by Patrick Dunn