Each week I post on my board the times that I am available for help. I am available for help before school any morning except for Thursdays. This is the best time for help. I put up quiz and test reviews on the mornings of quizzes and tests that are just like what the students will be seeing later in the day on the assessment.
If mornings are not an option, I can stay after school as long as I know ahead of time so that I can make arrangements.