I tend to be random with my bodily details.
Hands here, knees there. Mostly hair and bright eyes.
Brow creasemarks, necks strained especially, a limp, cheekbones
or the folds in skin as a body moves. Reaction takes, etc.
I kinda transitioned through certain phrases of writing
- only thoughts
- only action
- only description
Thankfully, now I'm a (better) mix of all! ^___^
Well, somewhat still in the description part.
Which is probably why this thread so appeals to me.

I don't mention weight usually because one, it's complicated
(what is a foot and can I say everybody weighs 50-60kg instead?)
and two unless, it involves sentences along the lines of:
"That kid looks like they weigh a quarter of a truck"
and or, "Wow, those veins man. Scary movie3.", thinking the units
exactly a person weighs is irrelevant in my book.

I do however, notice height is more of a staple in my
writing than others. Weird. Never thought of it before.
@vilageidiotx brought up something else I hadn't thought of before
until now. 

Maybe since (most, casual or otherwise) RPs are more about
telling than showing, prose is based mostly on telling about
the sort of impression you're supposed to get. 
Given people are different and imagine differently from individual 
to individual, @foster's point then, about keeping things nice and vague
to accommodate the other person- which I had admittedly, 
first scoffed at- fits better too..