I need help w/ fashion & looks! How can i take a great school picture?

School picture day is tomorrow. My freshman and sopre pics were blah but not horrible. I want my junior pic to look hot, y, and celebrity like lol :) I have short hair, my weight is average, and i am 5'8-5'9. What kind of shirt should i wear? What style? What color? How can i make my hair look perfect all day? How can i sit up straight in the pic without looking stiff? How can i look thinner in the pic? For some reasons my smile isn't that good. How can i make a nice wide happy looking smile? Any other advice would be nice! Thanks y'all for helpin!