1)Is the company licensed? 2)Are they insured?  3)Are they inspected by the state fire marshal? 4)All 3 above are required by state law. 5)How old is the equipment? 6)Is it cleaned before every use? 7)Are they using commercial equipment? 8)What happens if the owner gets sick does everything shut down? 9)Are they hiding there address from you? Usually a sign of a company that no shows.   10)Do they return calls in a timely manner? Especially on the rental day.