By Bill Fenton
When I started as a teacher, my overwhelming question was "what am I going to do in class tomorrow?" That question showed my mindset, thinking just one day ahead. What are the upcoming topics; how do they relate to the previous topics; how can I make all of this clear to the students? There was always a deadline looming just ahead of me. This was a nervewracking way to live!
When I sat down to prepare for a class, I typically used the following steps:

Read the appropriate section of the text.

Outline the major concepts from that section.

Create illuminating examples that were different from the examples in the text.

Write the presentation, based on the outline and my examples.
This preparation could take as little as 30 minutes for a precalculus class, or as much as 90 minutes for abstract algebra or some other upperlevel course. The time varied considerably, of course, depending on the topic of the day. Linear equations take a lot less prep time than linear transformations!
Since my institution has a teaching mission, I typically taught three or four courses per semester. It usually has been three courses per semester since I became department chair, but often this is three different courses.
Preparation time was consuming a large part of my life.
In the early 1990s, thanks to an intensive calculus reform workshop, I became a user and proponent of cooperative learning. This has affected every aspect of my teaching, especially the class preparation. I still begin to prepare for class by reading the section and outlining the major concepts, and I still write the presentation at the end. However, step 3 has split into two parts:

3a. Decide how best to involve the student groups.
3b. Create group activities, mostly based on illuminating examples.
The extra thought about how to get groups involved added about 15 minutes to each class' preparation time, though this decreased as I gained experience and expanded my repertoire of cooperative learning techniques. In total, a typical 50minute class was taking about an hour to prepare and this happened three times a week for every course.
At some point about a decade ago I decided to plan over a longer period than just tomorrow's class. Now I prepare for an entire week's classes of a course at one sitting. This has some real advantages over the daybyday approach. First of all, I have to assemble the necessary materials (text, references, calculator, software, etc.) only once a week.
Secondly, the startup time of getting my mind focused on the particular subject happens only once. I teach lots of different courses at different levels, from elementary statistics to discrete math to advanced geometry. It sometimes takes me a few minutes to adjust my frame of reference.
A real plus is that I always have more material ready to present in class, so I never lose time at the end of a class period. I also believe that preparing for a week at a time leads to greater connectedness from one class period to the next. It has become very natural for me to design presentations that introduce a concept in one class and extend it in the next class.
In Discrete Math, for instance, we define the concept of combination and develop the counting formula early in the week, then do some sample calculations and explore basic properties (such as Pascal's Identity) later in the week. This gives students time to digest the basic notion before working with its ramifications. In Operations Research, we spend one class drawing a project network and finding the critical path, then at the next class we return to the same project and do the PERT analysis. Presented in this way, the content of one class relates more clearly to the content of the previous and succeeding classes.
For cooperative learning purposes, planning for an entire week helps me incorporate a greater variety of inclass activities for the groups, which helps to keep the students engaged with the presentations.
A week's preparation takes me about two hours per course (again with much variation by course). It is necessary to find a block of time to do this, but the designated time is focused and productive, it is time well spent. I always have a real feeling of accomplishment when an entire week's classes are ready. Furthermore, the pressure of a deadline is gone for a while!
Time Spent: about two hours per course preparation each week. This varies by course and by topic, but the total time is always less than that for several separate preparation sessions.
Time Saved: about an hour per week per course.
Bill Fenton is Chair of the Mathematics Department at Bellarmine University in Louisville, KY. He can be reached at wfenton@bellarmine.edu.