I agree with the others above.
It is all about planning and being as efficient as possible. It certainly keeps you on your toes.
Watching, listening, picking up certain cues (most dentists have these when finishing up).
As someone said before - check your lists, always be one step ahead.
For instance, as my Dentist is finishing up - I am discreetly clearing away any items that aren't going to be used any longer (eg disposing of sharps) as he/she is polishing a composite without the need for suction, making sure any forms are completed ready, cleaning around the patients (very discreetly - you dont want them to feel like you are hurrying them or chucking them out the room!), Preparation of the next session as the last one is at an end, check you have everything you need. It just takes practice and once you have your own routine, this will help alot. I always clean from the chair light downwards (as aerosols rise up) and them move onto everything else - makes sure you use correct 'zoning' this should allow you to create small areas that are for clinical use which helps when clearing up and disinfecting ready for the next patient.
Hope this helps