How near are the facilities to your pitch? Good to be close but not too close!
How close is the children's playground (if there is one) to your pitch? Good to be close if you have kids, not so great if you don't (see previous note about kids getting up a 5am in the height of summer!)
Can you park next to your pitch? If not what are the rules/facilities for getting all of your stuff to your pitch?
Is there a shop on site? It's good to know what supplies you need to take with you.
Do they hire fridges? Or do they let you use communal fridge/ freezers (for ice packs)?
If you are going in a group find out how group bookings work e.g. can you all camp together and how do you need to organise this?
If you are taking a dog find out if this is allowed.
Ask about the checking in process especially if you are arriving late. Also how do you need to pay - not everywhere has a card machine.
Do you need to book? If you are going outside of school holidays you may well be able to leave it open and have more freedom about where and when you go.
Is there a washing machine? (very handy if you have children and are going for more than a weekend!!!)