Let’s assume your child has a number of things to do and is lackadaisical about doing them. You remind the youngster—to no avail. Time passes. Another reminder is forthcoming with the same result.
Rather than become increasingly stressed, have a chat. The conversation will revolve around those things that are to be done by the youngster. After listing them, establish a procedure for each—VERY SPECIFIC procedures.
For example, if the task is homework, the procedure should list exactly when preparations start, where the activity will take place, what materials will be used, and an understanding that there will be no distractions such as viewing television. If the activity is play of some kind, cleanup time and procedures are also listed.