Depends on my mood, sometimes I want to put on some makeup and do my hair to feel "prepared" and "professional", sometimes I don't even change from my pajamas.
But what I always do is 1) make sure my stomach is full, 2) fill my water bottle (hydration is IMPORTANT), 3) throw the pile of clothes on my chair onto my bed, 4) put on my headphones. Usually I listen to music or watch Youtube or Netflix or something while I draw, but sometimes I notice I've just been drawing with the headphones on for 2 hours and never pressed play. Concentration ftw!
Stretching would be so good, I'll have to stick a note on my monitor to remind me..!