A production manager told this to me once and I never forgot it.
I do believe that it takes time each morning for a crew to find the location and the coffee.
This is natural and expected, especially during a long schedule of days, however once the
company gets going each morning it has to operate for the rest of the day like a lean mean shooting machine.
Nothing makes production happier than hearing the cheery call of "Camera's Ready".
Ongoing and tight communication between the DP and the 1st AD is also very important in staying on schedule so that the actors are through wardrobe and hair & make-up and are ready when camera is ready.
Remember to rehearse each scene with the director and their actors first to establish the blocking, and then send them off to the glamour departments while grip & electric prep the camera movement and light the scene. During this time it can be easy to loose focus on the set, and a friendly loud and proud call of "Camera's Ready" is what brings it all back together.
Don't announce it if it isn't true, and try to say it as often as possible to help keep it all moving!