Starting your teaching career is an exciting adventure, but it can also feel overwhelming. When I first starting teaching high school science back in 2005, for example, I soon found myself struggling to succeed at (what I see today as) basic tasks, such as marking, lesson planning and managing behaviour. So many aspects of the job were completely new to me, despite the limited teaching experience I gained from the Army Cadet Force as a teenager. The reassuring news is that every teacher makes mistakes – it’s part of the learning process. To give you a head start, I will describe ten of the most common rookie blunders new high school teachers make (and, that I have made at some point on my journey!), along with some friendly advice on how to avoid them!