Justin, the easiest way to learn is to go fishing with someone who knows what they're doing. That's how I learned. I'm pretty busy until the end of September, but if we end up going on a trip together again, we can definitely do some fishing.
Bill,
I often fish a kebari on deep fast streams, and it works great when the fish can't/won't come up for a dry fly. I caught a bunch of fish out of the West Walker River and Carson Fork of the Stanislaus earlier this year on a black #14 sekasa kebari. There isn't really a wrong way to fish one, but keep in mind you are trying to imitate some kind of aquatic insect that is swimming around or emerging to the surface. So my default technique is to cast it into a plunge where the water is foamy upstream to get it to sink to the bottom fast, then bring it back to the surface with short pulses as it drifts downstream. You can also "dead drift" the fly where you don't apply any movement and simply let it move with the water. But, any kind of movement that gets you a strike is good; try experimenting with different techniques for 3-4 casts and see what gets some interest. This youtube video has some really good examples that give you a feel for the timing and how much to pulse the rod: https://www.youtube.com/watch?v=ItgHMloFezs&list=UUcTgnl5MvFJ9t95LD_C2H9g
Keep in mind that in moving water, I almost never have the fly in the water longer than 10 seconds; let it drift by while doing a few pulses and then cast again. Don't be afraid to make lots of casts. If after ten or twenty casts you get no interest, change your technique or move a few feet upstream or downstream.
Stealth is important here; if the fish sees or hears you coming, it's unlikely that they will take any kind of fly at all. So don't just stomp up right to the water's edge and lob a fly in. It's not so important on fast water with lots of cascades, but on slower water where the surface is smooth (e.g. Lyell Canyon in Tuolumne), I have literally had to crawl up to the water's edge and cast blindly to avoid spooking the fish. The further you get from a trailhead, the less this is a problem.
For lakes, you will find that the fish usually cruise along the drop-off between shallow and deep water. This way they can look for food that gets blown in (ants, grasshoppers, etc.) while still having easy access to deep water to hide in if a predator comes along. Most lakes in the Sierra will have an 8-10 foot ring around the outside where they are shallow then drop off suddenly to deep water. I try to cast around that boundary. For some lakes it's really far out and you have to pick a spot where a rock sticks out into the lake and just cast as far out as you can. Other lakes where it's closer to shore the fish will cruise within a few feet of the edge you can cast anywhere you want. For lakes, I generally leave the whole line lying straight out on the water and have the rod tip just a few inches away from the water to maximize the distance I can cast. This is opposite of fishing a creek, where you only want your fly and tippet to be touching the water.
It always pays to spend five or ten minutes just observing the lake or stream before you start fishing. Look for fish that cruise by or rise to the surface. The best time to fish lakes is just after sunrise and just before sunset, if a lake has fish and you're around at that time you will likely see hundreds of rises and you will know exactly where the fish are. In that case tie on your favorite dry fly and you'll catch a fish on nearly every cast.