What authorizations should an instructor have?

What authorizations to give an instructor depend on their responsibilities.  It is best to give users as little authorization as they need to do their job.  This helps to reduce errors and abuse in many organizations.  Some authorizations to consider are:

1. Scheduling for other users - This authorization is helpful if you want them to be able to schedule for their students.
2. Repeat scheduling - if you want an instructor to be able to schedule several lessons at once based on a weekly schedule.
3. Resource sysop - You may want to make an instructor a resource sysop of themselves (their instructor resource ID).  This gives them the ability to edit their own instructor resource.  If an instructor has management over particular aircraft, you may also consider making them a resource sysop for those aircraft.
4. Billing for instruction - If you want an instructor to be able to enter their own instruction invoices, you should make them a resource sysop (same as above) for their instructor resource.  
5. Super-user rights for overlay/cancel - Only set this authorization if you want instructors to be able to cancel or overlay other user's flights, including those not scheduled by them.
6. Access to Customer Management screen - This will allow an instructor to view information, such as expired BFRs or other dates to target customers to contact for training.
7. View contact log and edit comments - This would allow an instructor to add comments related to contact with customers.
8. Add Group Messages - If you want an instructor to be able to add messages viewable to all users.

These are just some of the authorizations to consider.  Check the authorizations page for the complete list.