From our experience, DS settles a lot better once we've said good bye and gone. Some night he doesnt want to come home!

In the mornings where he is a bit more clingy the staff are pretty good and will pick him up, encourage us to lkeav quickly (the longer we stay the worse he can get) and then they take him out to the lay area so he can see us leave for work and he waves to the us in the car as we go out the driveway.
Obviously different centres have different layouts but the idea is more to have a system that works for you so your DD will know what to expect each time you take her.
Sneaking back in for a peek or calling to check on her is a good idea too, for your peace of mind.