1. How long have you been in business?
   Longer established businesses stay open for a reason.
   
2. Do you belong to any trade organizations or associations?
   This question can be misleading, but if the answer is yes, then chances are they are a serious professional that cares about the betterment of their profession.
   
3. What packages do you offer?
   
4. What are your fees and exactly what does this include? 
   
5. What are your overtime charges? 
   
6. What is your payment policy?
   Deposit amount? Due when? Balance due when? What forms of payment?
   
7. What is your cancellation policy?
   
8. Do you provide a contract specifying your exact services and fees, including pick-up and drop off charges?
   Never, under any circumstances, should you fail to get a contract in writing.
   
9. How will the driver be dressed?
   
10. Are you fully licensed and insured?

Bonus Question: What can I do to make sure everything happens without a hitch?