During planning, a teacher should generate specific lists of what students should know (facts), understand (concepts and principles), and be able to do (skills) by the time the unit ends. Then the teacher should create a core of engaging activities that offer varied opportunities for learning the essentials she has outlined.
This idea of backwards planning is one that we will be engaging in as we begin to map out our Language Arts block on June 20. It's an excellent practice that can be applied on a teacher, grade level, or school level.