I never once describe my first person MC.
The only way I've seen it done effectively (without feeling like it was contrived and a trick of writing) is when the character is narrating a reaction to something of himself physically.
Such as: The new khakis were stiff and not nearly as comfortable as my well-worn sweatpants. I hated dress pants, which was probably a throw-back to childhood when I was too tall and thin for normal off-the-rack clothes to fit. My waist had filled out, but I couldn't help feeling that I needed another inch or two of fabric to cover my argyle socks.
or
I wish it still fit. The gold ring meant everything to me for years, but age has not been kind to me and as I stare at the fleshy plump sausages that used to be lean fingers, I can't help but miss the sparkle I once wore so proudly.
or
My eye color never concerned me, until I found out about the mailman and my mother. Indeed I was the only of my siblings with green eyes, and it so happened, Mr. McFeeley had green eyes too.
