While reading 5 Steps to a Professional PresenceI came across this great tip:
Before you enter a meeting do a 30-second detail check. Find a restroom and start at the top of your appearance; hair (remember you are seen from front and back), teeth (make sure nothing is stuck in them), ladies make sure no lipstick on your teeth and make up is blended, nose (especially if you have had a cold or sinus), check for stains, dandruff, open buttons.
Invest 30 seconds so that when you enter a meeting you have IMPACT!