First and foremost, dress like a grown man. Always look professional. I'm not saying a suit and tie everyday (would be nice though when you are spending a few hours at the mall or wherever just to recruit new clients) You are your best advertisement. Secondly, I am tired of seeing barbers with plain paper business cards. I'm reminded of something Mike Baisden said on his radio show, "When I get cheap business cards, I find the nearest trash can." They really do reflect your mentality and give a sense of the type of service that will be rendered. It may cost a little bit more, but come on man, not that much. Think of meeting new clients as if you were on a job interview. You are trying to be employed by these patrons. Treat everyone like a celebrity and you will find yourself building an empire.
In closing, whatever you know the least about in this industry, stop being afraid to learn it. So many female customers came in and just wanted the basic wash and style (about $45-$55.00) I had to learn the basics for styling women's hair (perms, coloring, cutting split ends, using curling irons, etc) and it has it paid off. So don't be afraid to join a cosmetology school where you will learn both. For the apprentice, look over the female stylist shoulder and learn all you can him/her. Hope this helps.
P.S Save your receipts for every dime spent. These are tax write offs.