Ensure that your policy around gum/phone is clearly stated in your classroom expectations and posted visually in your classroom

Teach your expectation at the beginning of the semester/year and review periodically throughout the semester/year (e.g., monthly activities that review the expectations

Provide class reinforcement system (e.g., points) that reinforce students for following your gum/phone policy. Allow them to trade in their points at the end of class. Use a timer and ensure students understand that they have to follow the expectations when the timer is up (e.g., spit out gum in trash can, phone off)

Address the behavior quickly and quietly (to avoid reinforcing attention seeking behavior). For example, nonverbally cue the student to spit out gum, put phone away, quickly and quietly verbalize what you would like them to do (e.g., "Phone please") and then walk away.

Do not engage in argument in front of the class or a power struggle. If the student denies or refuses, ignore and then discuss it with the student later (without an audience)

Praise students who are following the classroom expectations and remind the whole class of reinforcement system in place for those who are following the expectations