I knew I was in trouble during my first year of teaching when my principal gave me a lesson plan book. He expected me to turn in my upcoming week's lesson every Monday morning. Plan ahead? Me? I just don't work that way!
I tried as best as I could that year to submit weekly lessons. I was lucky enough to have submitted my lessons the week our staff irritated my principal so much that he entered a negative note into the file of each staffer who hadn't submitted their plans that week! But I can admit it - I'm a seat of my pants type operator. I'm lucky to stay a day ahead, let alone a week or a whole unit!
There was a short time during my first years of teaching that I actually made up monthly calendars! I would print out a schedule for, say, the month of October for Stats class with potential assignments, quizzes, tests, and projects listed for the whole 31 days. And I'd do my best to stick to that schedule! That would force me to plan my units and activities far in advance. I'm not sure when and why I dropped this system. I think it was when I switched schools in 2001 - in a new district, it took me a while to plan ahead for the new subjects I was teaching, and then I got moved from building to building and subject to subject so often that I just gave up.
I started at my current district in 2007, and in 4 short years I've now taught every regular math course our school offers - I'm the "catch all" guy. I've taught Algebra, Geometry, Algebra 2, Trig, PreCalc, Stats (these last 3 are stand-alone 1 semester subjects), and AP Calculus in this time. That's everything my district offers, aside from Tech and Business Math, taught by our Business/Math instructor. So I've taught 7 math subjects - my colleagues have taught 2,3, or 4 different subjects in that time period! My flexibility is good for my administrators and counselors making schedules, but it's tough for me to focus my craft on just a few select subjects.
Currently, I try to plan a chapter or unit at a time. I figure out what assessments I should use, which topics will take the most amount of days, and what special projects or activities I should add into the regular text we use. Sometimes I choose not to use the text at all, if I don't like the question bank for a particular lesson. Then I'll rely on other texts and sources I have.
I love to do special projects, and now that I'm no longer teaching on trimesters, I have more time in the year to assign them. Simple activities like taking a day to make tessellations in Geometry, and doing stats measuring experiments in class I feel encourage students to explore learning math in different ways.
There have been days this year (Mondays?) where I've walked into school 20 minutes before my first class with no clue what I was doing in class that day - and yet since I've taught such a wide variety of topics in my career, I feel very confident on finding different ways to introduce new material to students. But being organized and planning ahead always works so much better!