I have just been on the phone to my mum to ask her exactly the same thing! She used to run a nursery and is still on the board.
She said to ask about the following:
If you can ask the staff not just the manager about their policies such as staff to child ratio.
Ask about daily routines and whether they can accomodate your own childs individual routine.
Make sure they have progress files for children which contain a record of their milestones and often photos
Ask whether they keep a daily diary for each child eg do they record what they have eaten, how many dirty nappies etc. If not ask whether they would do so for your child
Ask about outdoor space
Ask about one to one time
Ask about how often the toys are cleaned. For babies they should clean toys daily
Whether they have a profile for each child (eg dietary requirements, whether they have a dummy) and how this is communicated to staff.
Be more worried if the place looks too sterile rather than a little rough around the edges. If the toys are a bit battered this means they are used!
I think that was about it. It will be my PFB and I am anxious about leaving him at nursery even though he is not yet born yet! Nurseries near me get booked up very quickly.
Hope this helps.