Be sure to inquire about the staff turn over rate for the pre school. While many pre school teachers will move and change careers, if more than a reasonable number of teachers or staff leave per year this can be a sign of management and administration problems.
Look for playground areas, art rooms, inside play areas and physical education areas inside the school facility. These should be separate areas and not just contained within the same room. Do they seem to be well supplied? Are they well used and are they well set up to be easy for children to access?