Early on I realized that flexibility is the name of the game. There may be 180 days of school, but snow days, assemblies and sickness can wreck a tightly scheduled plan. Over the years I've developed a system for organizing lesson plans that gives both flexibility and the assurance that we will cover all the important content areas.
First, I list out all the lessons for every class. Usually the curriculum will have a list and sometimes I use the table of contents. When I have developed my own curriculum, it may take a year or two to feel out the pace. Ideally, about 95% of your class time should have a plan, including projects, review and testing.
I then spread the lessons onto a calendar. Several of my classes are on a rotation so it's important for me to see when they fall. Monday classes miss several weeks in the winter because of holidays. I can either adjust their flex time, reduce their review days or reschedule them on another day of the week.
The whole process can be time consuming. It's also frustrating when an unscheduled field trip takes an entire grade level away the day I had a fabulous lesson planned. So the calendar view is more of a guide, while the lesson list functions like a checklist. When the two begin to differ, I know that my pacing has fallen off and I can look for opportunities to bring everything back in line.
For me, the content is always more important than getting through the material. I don't want to hold students back or rush them through just so I can stay on pace. It also helps to have some optional extra content to add in. I may not want one class to get farther ahead of another section, so it's good to have supplemental material for them to work on.