I'm aware of zettai ryouiki. It's the amount of skin between the skirt and the socks. Some prefer a large amount of skin, some find it super appealing to have literally just a bit of thigh peeking out. I'm the latter, so if I really want it I'll make her socks go way up, leaving a gap about two fingers.
Is an anime trope, I know.
I also like ankles. The less ankle the better, but not to the point zero ankle. Problem is I can't draw ankles and feet yet. That's gonna be homework for me.
Also problem is that I can't make BOTH zettai ryouiki and ankle flashing simultaneously…wait no I can. I've seen it. Okay that's an Idea I'm gonna play with today.