What not to do when cycling?

What should cyclists avoid doing while cycling to ensure their safety and the safety of others on the road? Is it important to wear protective gear, such as helmets and reflective clothing? Should cyclists avoid using their phones while riding, or is it okay to check messages at stoplights? What about riding against traffic or ignoring traffic signals - are these behaviors that should be strictly avoided? Additionally, what are some common mistakes that cyclists make that can lead to accidents, and how can they be prevented?