First, I agree that the higher you go or the farther in you go, the better. The odds favor you for a couple reasons. I think the idea of "dumb" fish has a great deal of validity. Hike far enough in and you'll be stalking fish that likely have not been caught and released. While I believe in and practice C&R, I can also see where this generation of fly fishers are conditioning the fish... maybe not making them smart, so much as wary. Also, You'll find the water levels generally a bit lower and clearer -- "...the better to see you with, my dear". I've found it much easier to sight fish in the higher elevation streams than say at Metcalf.
I would have to say that stealth is crucial at any elevation or distance. Keep in mind that we humans are just one predator that these fish have to contend with - and we tend to be the clumsiest.
Finally, take a good hard look at the size of your offering. I've heard and read a great deal that says, basically, that size is a more important factor than even color. I know that on the tailwaters around here, the difference between a size 20 and a size 22 midge can mean the difference between a day of no fish and a day of fish. So next time you're working a section of stream, before you move on, convinced that there are no fish there, take a five to ten minute break, then try dropping down a size or two in the same fly and working the section all over again - starting with the closest in cast and working your way out and across.
As for the proper tongue placement... I've refined it a bit and you may find it helpful. When fishing for browns, I hold my tongue out the right side of my mouth. I think this is why so many people have a hard time catching browns in the park. They assume that if you can catch a rainbow with your tongue hanging out the left side of your mouth, then it'll work on all fish species. I don't think so. For Brookies?? I just keep my mouth shut and pray!!