You could offer to give the most popular person in the class a free stringing (if that is a nice looking person of the opposite sex alls the better). Maybe even offer to give the next 5 people in your class who ask you a free stringing. If you do a good job hopefully you'll get some word-of-mouth business as a result.
A Head Microgel Radical, a Neos 1k, and a Silent Partner Star. Life is good.