Make sure they know what to expect.
Make sure they can go to the loo, dress themselves and wipe their own noses.
If there is a uniform, name EVERYTHING. It WILL get lost.
It's good to walk to school with a friend if possible.
Show a huge interest in the pictures and so on that bring home.
Don't interrogate them, they'll tell you in their own good time.
And above all DON'T CRY OR EVEN LOOK SAD when you wave them goodbye. Children who weep are often picking up the parents' anxieties about separation.
What was the first film you ever saw in a cinema?