My hair is:
(a) fine (actual strand size and texture)
(b) very low density (lots of scalp shining through) and
(c) hereditarily thinning (mostly in crown but creeping into edges)
Actually, all of these are due to my family/hereditary background. My mother has very fine, low density, and thinning hair; my father has low-density and thinning hair; my paternal grandmother and maternal grandfather both had fine, low-density, and thinning hair. Many uncles and aunts are in the same boat(s). A dermatologist looked at my scalp and told me when I was 16 that the only thing I can do is Rogaine.
I am not happy with "the situation."
Not so deep down, I do not believe that the Jamaican Black Castor Oil, scalp massages, and all the other products and techniques people hype will have any effect on my 3 issues. I know they are programmed into my genes.
So, the best I can do is camoflauge:
1. When my hair (which is 3-ish curls) is 2-3 days out from the last wash, it gains enough puffiness and frizz that, put together, it gives a nice Scary Spice-ish impression of volume and high-density.
2. I do a curly version of a comb-over: I can't get a comb through my hair when it's dry, but I can take the long spirals growing out of my hairline and flip them back over my crown to hide it, fluff them up a bit, and clip them in the back so that they create a bouffant-ish "bump."
As a result of these two strategies, when I state that my hair is actually thin and thinning, people go "You? Oh noooooo. You have SO MUCH HAIR!"
It's nice that they don't believe me and all...but if I lose even a few strategic hairs at my hairline and edges, the scalp of my crown will be exposed once and for all, with nothing to hide under.
I'm sorry I couldn't offer more help!