Specifically:
>variations
>exceptions
>things you ignore and why
>things you find very important and why
>stuff that's situation dependent

I've read up on a lot of LNT, plus had a good bit of direct experience in the woods, but like anything in life (and especially in the Wilderness), it's more a set of general guidelines than hard-and-fast rules.

Things I think are important:
>Always pack out trash.
Everything. I bring a bag for stuff I find along the way, and pick up as much of it as is reasonable. Exception: anything somebody might have wiped their ass with. A wise man once told me to never touch clothing on the side of the trail. It's there for a reason.
>Dismantle and rehab fire rings and campsites that are right next to high-use trails or water sources.
Fucking hooligans.

Things I ignore:
>Go 100+ ft from trail to piss.
Fuck that. I'm lazy. Sometimes it's really hard or dangerous. Sometimes leaving trail would do more damage to sensitive ecosystems. And the trail is already a heavily impacted area. But mostly I'm lazy. I'll go off trail if it's easy, or if there's a lot of traffic.
>Bury poop 6-8 inches into mineral soil.
I have almost never been able to dig 6-8 deep into mineral soil without striking lots of roots or rocks, and a trowel is one of the few luxury items I usually carry. It's especially hard to do this under the time constraint I'm usually under when I finally decide I have to poop bad enough to quit hiking or get out of my sleeping bag.
>Bear canister or hang.
Sometimes I don't. Fuck bears.
>Sleep 200+ feet from trail.
Usually I do, but I worry more about how impacted the site looks and how visible it is from the trail. If I find a good flat spot out of view, but kind of close to the trail, I'll crash there if it doesn't look like a lot of folks would use it. This mostly if solo and cowboy camping Never in groups>2. Quick rehab in the morning.

Things that are situation dependent:
>Dismantle and rehab existing impacted campsites or use them?