It's just me picking whatever's closet to my hand position at the time. If I'm writing I'll just grab my glasses by the edge of my right hand, if my hands are in front of me I'll push up the bridge using my middle finger, and if I can't see at all with my glasses at whatever range I hold it by the edges of the glass itself and adjust them from there. For me, it's all just a logical extension of what my hands are doing at the time I need to adjust them.