Marker ink must be readable. The slate must indicate camera card number (roll number), sound card number, frame rate, scene number, take number, and MOS or SYNC. If using multiple cameras, identify which camera: A camera, B camera, etc. 

Camera must frame and focus on the slate, not frame for the shot.  Slate must fill ¾ of the frame. If in dim light, set up a slate light.

Slate person starts with clapper open. If possible, not right in front of talent’s face.

AD says: “Roll sound.”
Sound turns on recorder, says “Speed.”
AD says: “Roll camera.”
Camera calls “Rolling.”
Camera says “Mark it.”
Slate calls out scene and take number and claps slate briskly.
After clap, hold slate in frame for a beat to insure an un-blurry frame of closed slate.  
Remove slate.
Reframe and refocus for shot.
Director calls “Action”

The scene plays out until the Director (and ONLY the Director) calls “Cut.” After each take, adjustments are made by talent and crew.

For tail slate at end of scene, hold slate upside down, call "tail slate," scene and take number, and close clapper.

If MOS (mit-out sound / without sound), with hand at hinge, hold clapper wide open with information easily readable in frame. Circle or point finger at MOS.  DO NOT CLAP MOS SLATE.