I was introduced to this when I did a semester of student teaching in a New York City Public School. Back then, it meant sitting down with an academic calendar in front of you, scribbling down some notes here and there in your planner, and flipping through some textbooks hoping to find appropriate activities for your class. Knowing what you'll be doing with the kids is very important.
The next time I encountered the concept of Lesson Planning was during a teacher training program in New York. Then I learned that there are a gazillion ways of creating a lesson plan. Basically choose a template that you're comfortable with and use it to guide you through the day or week, so long as you have the same components: objectives of the lesson, materials/tools, procedures, means of assessment and reflection. Be prepared!
