There are several things that you may want to include in a homework planner:
Calendars: You may wish to insert a monthly calendar followed by planning pages as well as a calendar for the entire school year for a quick over view.
Planning pages: With the day of the week, date, and room for each subject that your child is taking.
Project Goals: You may want to add a small place for your child to write in goals to help them accomplish larger tasks, such as research papers, so they can spread the work out over a period of time and not be too overwhelmed the night before a project is due.
Class schedule: Including a class schedule in the homework planner, typically near the front, will help your child to keep on schedule during those first few weeks when they are adjusting to a new schedule. It will also be a helpful reference when scheduling doctor's appointments, etc. since you can easily reference which classes the appointment may conflict with to check for test dates, etc. that you may not want your child to miss.
Contacts: You will also want to include a small section for contact information for things like your work and cell phone numbers, a homework hotline number or class website for checking on missed assignments, coaches contact information or other important numbers.
Extracurricular Activities: Do not forget to include a section each week for writing down practice schedules, study sessions, rehearsals and other events associated with the extra curricular activities that your child enjoys. You may also want to include activity schedules for the year as a handy reference for games, tournaments, plays,etc.
Records: Another useful section to add to your child's personalized homework planner is a simple place to keep a record of their grades for the term, absences, etc. so that you can both monitor your child's progress and catch any potential downfalls.