A "Do Now" activity is designed to get youngsters to "settle down" at the beginning of class(es).  The activity should require them to get out pencils and materials that will be used in your lesson.  The task is usually written on the board and the students are to start on it as soon as they enter class and go directly to their seats.  You might require that they answer some review questions from yesterday's lesson.  It might require some initial thoughts on some questions that will prepare them to discuss the material in the lesson today.

One teacher uses a "mental minute" at the beginning of class (immediately after the bell rings to start the period).  Students are given a worksheet that they attempt to complete in one minute.  The teacher says "go" and students undertake the challenge.  They are quiet and focused for that first minute.  The review of the sheet leads into the topic of today's lesson.

You have one minute to list 5 words that rhyme with "Orange".  GO!!