(See my blog for the way this response SHOULD look: vonfaustus.blogspot.com, if unaware.)
(I was asked a question by a beginner about how I find the Genius Loci, and what I do. I actually answered the question, and then formspring had some odd error which erased the question and my answer. Or it's stuck in the digital ether somewhere, and will appear later. Don't ask me, man. The picture is from "geniusloci.co.uk". I love the site. It's very pretty.)
First, and I don't want to sound like an elitist asshat, keep in mind that what I'm about to discuss isn't actually for beginners. I'll highlight the issues you may have to contend with as I progress. Also keep in mind that the process is lengthy; which is why you don't see near constant updates of sigils for the Genius Loci, and so forth.
The first issue was finding the Genius Loci. My primary operative theory in this work is that any active location, in terms of having a fully sentient spirit sitting atop it, is going to be fairly easily revealable. Be it the haunted house down the street that gives you the creeps, or the aging Victorian manor at the edge of town that seems to be filled with mystery. Since the spirit and the place are fundamentally tied together, this should quite clearly make such locations both obvious and subtle. Once you start seeing the locations, it becomes easier to find them.
The problem was how to locate them. I came up with my own trick: wandering aimlessly. As I wandered through the city, I'd crank up the music on my Blackberry and ride the trance out. This isn't, mind you, a full “vision trance” or anything like that. For the most part it involves wandering through the city in a light trance, retaining that trance, and keeping the words: “one of these things is not like the other; one of these things does not belong” running through your head. At least until you start to see what doesn't belong. This isn't exactly the most scientific method.
Realizing this I began doing divination readings on the spot. I'd use my cell-phone camera to take pictures of the street and locale (so I could remember it late), and kept four coins on hand for the divination. I've also brought my Runes with me a few times. The divination technique I like for this is Obi. I like Obi because I can cast four coins on the ground, photograph them, and then continue the reading elsewhere from the first point. To most people it looks like you've just “accidentally dropped” four coins, which when operating in public, is... good. Pull three runes out works too. The questions I normally ask are: “is there a spirit at this location?” “Would this spirit be well disposed to my intrusions?”
After that I hopefully have a few locations to work with. These are normally: parks, old houses, old theaters, and so forth. (There's another method for doing the same thing that's easier, which Ryan Valentine advocates: find out where the oldest buildings in your city or town are. And then go looking for spirits by trying to energize the location with a ritual; this has it's own disadvantages, and I'll discuss it in my forth-coming essay “Seeking Paradise in Exile.” When you'll see that essay is beyond me; the e-zine it was for collapsed before it could get off the ground. But the editor has offered to turn the entire essay into a nice looking PDF for me as soon as I'm done. So it'll be easily in everyone's hands eventually.)
After this what I'm doing stops being accessible to the general public. I'm working with DeusExMachina of the old TIAMAT-L days to narrow down the techniques I use and give them to the public so they can use them. But basically... Eventually, I return to the location. I bring a paper and pencil with me. I settle down and meditate; initiate trance, and then automatically draw a sigil. The technique for automatic drawing I use has been written about by Austin Spare here. To say that this technique is hard is... um, actually, a bit of an understatement. I can't quite automatically draw; I've produced automatic squiggles, and these days they are certainly automatic sigils. Though they don't look quite right.
Following that, I take the sigil home and evoke it into the astral temple. When doing so, I'm always sure to set down a circle in the astral temple. (Beginning to see why I say the process is lengthy?) This is for two reasons: even if my divination attempts on the premise are wrong, I still have a place of shelter. I can test the spirit and gain a name from it while in the astral temple; and the evocation process is easier than it is in real time.
Now that I've made all of that sound easy, here's what can go wrong!
The spirit may attack you.
The spirit may attack you.
The spirit may attack you. Keep an exorcism or banishing ritual on hand. I think I've made that clear enough.
The sigil may not be that of the spirit; it may be from your internal “Alphabet of Desire.” Sorting between the two if you've never worked with either is a pain. Wait for the better, non-automatic technique that Deus and I are working on.
Some locations are harder to initiate contact with than others. When the basic 'meditate and draw' fails, you've got a choice: abandon the location and the potential of it's spirit, or try Incubatio or Incubatic Dreaming in the location. This really only works if it's a park or “open house” though, as most people don't want you sleeping in their yard. I'm working to see if I can activate runes before I do it that stimulate both protection and aid in the contact process. But my handle on the Futhark is, at current, very tenuous. (My apologies! I seem to be lacking where it matters, and full of technique where it doesn't. Blame the “oooooh, shiny!” mentality of Chaos Magick for that.)
You need to know your invoking and banishing pentacles. Seriously. When testing what the spirit says, projecting either the correct or opposite element on them bolsters or disempowers them. This is one of the easiest ways of discovering if it's lying to you or not. The lies normally begin with the elemental plane (and most GL I've found are tied to 'elemental planes' in some way, even if they can't explain to my how) that the spirit exists next to or parallel to. The other lie can be it's name.
There's a lot more, but... I think most people will get the jist of what I've written.