When hiring a contractor it is always best to hire one who is personally referred to you by someone you trust. Hiring through ads or phone book is hit and miss. Check with your local paints stores, they know the good guys from the bottom feeders. Go to the stores that sell the high quality paints like Benjamin Moore(nonpareil), Pittsburg, Sherwin Williams or Glidden. Don't go the the big box stores for referrals, the people there don't know squat!
These are some fantastic questions to ask and I particularly like the one that is concerned about safety for the painters. After all, if you have a large home and you’re hiring them to paint the exterior of that home then they’ll likely be on scaffolding. Because of that, you need to make sure that the contractor not only provides appropriate safety training, but has the correct liability insurance as well.