Aside from the obvious, ie good workmanship fair pricing, dependability, think about your image. Arrive in a decent truck, clean on the outside organized inside just incase customer happens to look in. If you arrive in a jalopy with material and tools piled up inside this will reflect how you will treat their home or business. Wear good work clothes not torn jeans and sneakers. A little effort on this end goes along way with first impressions. One thing that I think is very imporatnt is to know that it is ok to say no to work. If you do not feel comfortable with a client at the initial meeting you might try meeting again. If you still feel uneasy it may be time to walk away. One point to remember is try to avoid taking on more than you can handle. Nobody wins in this situation and the only thing you will gain is added stress.