OK, let me start by saying I'm NOT an expert by any means, but I'll give you my thoughts on the whole lean/not lean thing..
Some things are easy, like you said, chicken breast, fish..basically most meat I consider "not lean" lol but here are a few examples of things I do consider lean, besides the obvious
-Steak that has to be marinated/tenderized/cooked for awhile to be tender like outside or inside round (basically the marbling (fat) in the more tender cuts is what makes it tender. by buying a cheaper and leaner cut you are saving money and calories..and you don't really have to marinate it forever if you slam it or cut it really thin

-boneless pork sirloin chops - you know , those ones that look kinda like a kidney shape..and have no fat on the edges? Some are dark meat and some are light meat..i think center cut vs whatever cut..the darker ones are dark meat..but the light meat I consider to be a lean cut
- lowfat ground turkey or chicken - some of course is made with dark meat but some brands actually state on the label the percentage of fat in it so you can make an informed decision
ALthough I LOVE meat, I am really finicky about fatty meat, grissol, marbling etc, and i hate the feel of it in my mouth. Whenever we have meat that is not of a leaner cut my plate still has plenty of "remnants" when I'm done, while dh's is licked clean..lol He must wonder what my problem is. As a matter of fact, someitmes when we get a roast or stew meat and it turns out to be grissoly on every piece (like thru it) I won't even eat it, or I'll give up halfway through. I just cannot be bothered...sometimes you can't tell if a roast is going to be grissoly or not before buying it...anyway my point with that is that I kinda trust my tongue on it, if it's the type of meat I can enjoy the whole piece without weird remnants than it's all good. If I have to prep and scrape before and during ..then its a fattier cut.
Wondered about the 1/8 inch thing too, it must be that some people actually eat the fat beside the meat?? UGH!! Otherwise if you're discarding it what does it matter?
If you want to be more precise you could get one of those tiny purse size counters with fat/pro/carb counts and just spend a couple minutes browsing the different groupings ..or if you have any old low fat diet books kicking around or even maybe go on the heart association's site and they may have lists of meats that are heart healthy and not-so much..lol
I tend to really not worry about it and unless the item was literally dripping with fat (I think ribs and fried chicken are the only 2 uber-fatty meat products I can handle) I would get what I wanted in a restaurant ..make mostly chicken and leaner steaks and pork at home and who cares if some of your selections are a little fattier, it'll make you more satisfied anyway and it's better than over carbing it..at least you won't wake the cravie monster
