you can ask them if its ok for you to sit and watch because you want to see how the daycare works and if it's the right one for you. if they say no, go to the next daycare. they should have no problem with letting you observe their dayly activities
Ask them about their menus, play time, activities, nap time schedules, displine.
Check out the place too. If it seems dirty, the toys are old and falling apart, not a good idea. Safety wise anyways.
Ask them what the turnover rate is. If kids are constantly coming and going, I see that as a red flag.