Handheld shots may work in a crowd, but seldom. The camera is not a passive instrument, but should be used as an active instrument of revelation. There have to be modifications to help the camera, but the challenges are what make movies exiting. Don't take untried equipment out on big shoots. All equipment should be tested at base before taking on location.
Golden rules are to foresee the worst, and test it first.
The camera assistant must keep a camera log and the sound person a sound log. 2. slate and take number 3. The director's problem is sensory overload. Part of his problem is being the sole audience for each actor. Tricky camera set-ups should be rehearsed in advance, and the correct props and costumes ready to go.