This exercise is intended to strengthen your powers of description, but I'll warn you, this one might be a wee bit hard. I want to you to pretend to be a writer sitting in a coffee shop and who should walk through the door? But you, of course! Describe yourself as a stranger sees you. (Be kind!)
And remember to not just focus on a physical description - how you dress, how you move, what sort of things you carry with you, all contribute to the overall impression you make. You are far more than just a height, weight and hair colour. And this writer that is watching you has above average powers of observation - what do they see?