How far apart do you position your speakers ?

Speaker and room dependent. Gives the speaker and the room dimensions and we might be able to offer some guidance, though often, that will just be a starting point.

I thought the rule was the speaker width apart should be as wide as the distance from your seating position to the speakers? So if I'm sitting 12 ft away from my speakers they should be 12 ft wide as best as you can. As for distance of the rears of the speakers from the wall I just follow the instruction manual as best as I can. Right now from the rear of the speakers it is about 8" from the wall.

Triangulation is a rule of thumb, and usually much better than what some might do without any guidance. But getting it right for any particular speaker is dependent on the speaker, the room dimension, room treatment, and sitting position. But as a starting point the equalateral triangle is a good start, but that sound incredibly close to the rear wall and some [?] most [?], certainly not all, speakers will have a hard time with stereo center fill if they are 12 feet apart, more than 7 with mine and the image density is reduced, though it does make for a "wide" soundstage. The rule of thumb works, but rarely ideal - it is a starting point.

1.5 to 2 times the height of the speaker is probably just a coincidence because many floorstanders are in the 3 - 4' height range, which would put them 4.5 - 8' apart. That's about the distance of an EQ triangle in many small to medium rooms.
Get a pair of Maggies or Logans in there and it doesn't work.
I usually move them into the room to where the bass and midrange sounds good, then move them apart until the center image begins to get thin and diffuse, then move closer. This is usually pretty close to an EQ triangle but a little wider apart.

Jim Smith (of "Get Better Sound") says that the distance apart should be 83% of the distance to your ears. While I don't embrace all of his suggestions, this rule has worked well for me in the past. In fact, in placing my speakers via trail and error BEFORE I read Jim's book, I ended up with an 84% differential.