My hair is naturally fine textured, w/ medium density, so this how I can tell the following:
a.) coated--A dead giveaway is my scalp. If my scalp has a yuck feeling even if my hair is relatively clean, I know that I have put too much product on. Also, it looks finer/thinner than normal and if I rub my hand over the surface and my finger ends up greasy, I've gone too far. Usually when my hair is coated its more of a 'feel' than visual appearance.
b.) needs clarifying--my hair, ESPECIALLY the ends are unusually crunchy. It seems like even the best of my products don't work anymore, and a day after I wash and condition its dry again even if I've moisturized properly etc. I can't get it shiny and it looks dull, dry. I also begin to notice breakage. Clarifying corrects this problem for me because the buildup is preventing moisture from reaching the hair strand properly.
c) Weighed down--no bounce or volume, has that stiff appearance OR flat, little to no swing. Pretty much goes hand in hand with coated.
this is my personal view on these....HTH!