I have been involved with the running of our family nursery for many years. In my experience the following are the things that really matter in a nursery:
- Being friendly and welcoming to children and parents.
- Providing a caring environment where children feel comfortable and safe.
- Providing a large variety of fun activities for all ages.
- Carrying out an up-to-date educational
- Providing healthy and varied meals.
- Following good hygiene procedures.
So in practical terms, I would recommend to ask about facilities, education, diet and maybe staff-ratios (as you mentioned). And while you're looking around, see if the kids seem happy and entertained, the staff seem friendly and are engaging with the children and that the place is clean and tidy. Also, I'd recommend having a good look at the wall displays- they should give a good idea about the quality of the teaching syllabus. And most importantly- "what is your gut feeling?"- would you feel happy leaving your child there?