When I was a wee slip of a jumped-up grad student,  I was fortunate enough to have faculty who were invested in doing mock job market activities. We workshopped CVs and cover letters, had mock interviews (complete with appropriate attire) and job talks, the whole nine yards. It was a very popular series, and saved more than one of us from more than one disaster.
Around that time was just when the "statement of teaching philosophy" was just coming into vogue as a part of the job search package. Suddenly, every search committee wanted one. Problem was, since it was so new, no one could figure out what it was -- not even search committees who asked for it, I suspect. But one of the faculty mentors in our job search series made a comment on one draft statement that has stuck with me. Reading how this faux applicant talked about his emphasis on primary sources and class discussion, the faculty member said, "This is a good teaching methodology, but it's not a teaching philosophy."
So, what's the difference?
Now, before I jump into that let's get two things out of the way. The first is that everything I say from here on out is in the way of general advice. But if your job ad or search committee's instructions say that your teaching philosophy should feature a discussion of A & C, then fertheluvagod, ignore my advice and write about A and C. And thank your lucky stars that you are working with a search committee that is clearly communicating what it wants to see. This is the kind of department you want to work for. Don't screw it up by ignoring their instructions and sending them something generic just because some random blogger told you that this was what a teaching philosophy should look like. Got it?
Second, you'll hear a lot from certain quarters how the teaching philosophy is a BS exercise, that most committees ask for it as a sort of fishing expedition with no clear understanding of what they want to see, and that everything that everyone says is all exactly the same... basically, comments that might encourage you not to take this seriously. Mama Notorious is here to tell you no. Okay, in some cases, some of this might be quite true. But in jobs where teaching is a significant part of the mission, your ability (or not) to talk about your approach to teaching shows the search committee that you have thought deeply about how to be effective in the classroom, and that you have a sort of a vision that goes beyond the syllabus and "I assign lots of primary sources." So if your search committee asks for one, take it seriously. Spend some time on it, just as you would spend on a cover letter.
Okay, with those two caveats in mind, as well as the usual YMMV, I'll talk about my approach to teaching philosophies, and I hope that people who have served on search committees that have asked for these will also jump in on the comments and add their perspectives.
Keep it brief: Just like you wouldn't go on and on in your cover letter, you want your teaching philosophy to be no more than 1-2 single-spaced pages (again, this is assuming that your committee hasn't given you specific page limits).
Remember that teaching methodology isn't the same as teaching philosophy: What you do in class is important, but why you do what you do is really what the "philosophy" part of it is.
Philosophical points can be abstract, so back them up with a concrete example: This is where you can -- and likely should -- weave in a bit of methodology. So you have a principle that guides your teaching or course design or whatever. Then you give an example from a course you have designed or taught to nail it down.
Beware the Scylla and Charybdis of edu-jargon and treacle: Too much Bloom's Taxonomy is going to cause lots of eye-rolls among faculty members who have sat through far too many meetings where far too many folks have tried to force-feed them the latest technological innovation or educational model that will save us all, at least until 18 months from now when the next one comes along. Likewise, sounding like you've watched Dead Poets' Society too many times may cause them to lose their lunch. A knowledge of new directions in the field is good (even essential if you get an on-campus interview and find yourself across from a provost who wants to know how you scaffold your courses or what your take on the flipped classroom is). So is idealism -- in fact, if you are an ABD or a freshly-minted Ph.D. and you're not a bit more idealistic than the people interviewing you, there'd probably be something wrong there. But don't overdo either one. Too much in either case and you risk coming across as someone who is saying things that someone told them Good Teachers believe. Be enthusiastic, be engaged, but above all, do not pull out your trowel and start laying on the bullshit. Be true.
Avoid pretentious references like "Scylla and Charybdis." 'Nuff said.
A teaching philosophy should not read like a course catalog, replete with a list of every course and every topic within each course. On the other hand, it should, along the way, give an idea of the range of courses you could teach. In this, you will want to slightly tailor each one to the school you are applying for. If the job is going to call for you to be a generalist, then you will want to emphasize the breadth of courses you can teach. If the job description says that, in addition to courses in your field you will be responsible for teaching the Early U.S. History survey, then your statement ought to address your approach to intro-level survey courses. Just like in your cover letters, you'll probably be working from a general template or two, but then make sure that each one is targeted towards the job you're applying for. And again, don't get all list-y. Remember that the approach/philosophy is the main point; weave in mentions of your courses as you deliver that main message.
Sound like a lot of work for a document that hardly anyone asked for 15 years ago? It is. So here's my last bit of advice: Just like the cover letter, the teaching philosophy is a work of writing and a presentation of who you are as a teacher and what you would bring to their department; give it as much attention as you would that cover letter. Revise it, show it to people, revise it again, have a beginning, middle and end to it, polish the prose. And make it honest.
Thus endeth my take on this. Now, for those of you out there who have sat on search committees and read more than your share of these documents, what would you advise?
 And I was always a jumped-up grad student whose reach was always, if not exceeding my grasp, then certainly preceding my grasp by about 18 months. I'm sure the faculty of my graduate institution could only roll their eyes and shake their heads at times.