I like to split my questions up into ones to ask before going to see the place, and others to ask while I'm there. The "before" questions are the deal-breakers: is it in my price range? How much turnout do the horses get summer/winter? What riding facilities do they have?
If there aren't any deal breakers then I go see the facility and try to get an idea of what the average day is for the horse- when they get fed, when they get turned out, when they're brought in, etc. (I try to get an idea of how regular they are with the schedule, but it's hard to know for certain) I look into the horse's stalls and check if they're clean, if they have water and hay to munch on. There may be one or two older horses that might be a little ribby, but for the most part the horses should all be in good weight and healthy looking. All should have properly trimmed feet (even if they don't belong to the BO, it speaks poorly of the facility if they allow boarded horses to go neglected). Look into the feed room- it should be relatively neat and clean without signs of rodents, bugs, or other vermin. The arena footing should look well maintained and not be overly dusty.
As for actual questions-
- How is turnout handled? Do they turn horses out individually if desired? For groups, how do they handle introductions? When is the weather considered "too bad" for turnout, and do they do anything extra for the horses if they can't get turned out (extra hay, extra stall cleaning, etc.)?
- How much hay/grain they typically give horse? Are they willing to adjust it as necessary if the horse is a hard keeper?
- Have they done a nutritional analysis on the hay (most have not, some don't even know what that is)?
- Do they give a discount if you provide your own grain?
- Will they put fly masks and blankets on/off as needed, and if so do they charge extra?
- Is there a wash rack? Does it have hot water?
- Is there a bathroom?
- Is there a washer/dryer?
- Is trailer parking available? (Look around and see if it's easy to get in/out of. If it's not, will they park the trailer for you?)