about the 'what stall is the cleanest'.. I read it's the one in the middle.
I guess whatever one you choose is fine. I like the one with a window because I hate breathing in public bathrooms and even though you can hardly ever open the window I feel better next to a window.

My strategy: open the door with my sleeve, or push against it with my weight and open with my elbow (not in summer as it's bare skin), enter, somehow lock it, usually I have to touch it to do this, then hover!, flush with my pinky or toilet paper. Washing my hands repeatedly (with a disgusted face expression I cannot help but have) and then open the door the same way as when coming in.