If you are in sales, and deal directly with the public on a daily basis, one of the most important assets you can have will be your smile. This may be a "no brainer" or sorts to many out there but I run into people trying to sell me stuff every single day who do not understand how important it is to look approachable and friendly. If you want to make it in sales - you need to understand that most people (if not all) want service with a smile, and in many cases it can make or break a sale.