Working as a supply teacher in a school can give you a lot more flexibility than a full time teaching job, but it can still be difficult to stay completely on top of your work. You will often be working in unfamiliar environments with different systems and expectations.
Keep a well-organised bag with essential resources that you take to every placement. This should include emergency lesson plans, basic stationery, a timer, and any resources you regularly use.
At the end of each day, take a few minutes to write notes about what you taught, any issues that arose, and anything you need to hand over to the regular teacher. This professionalism will be noticed and appreciated.
Stay on top of your professional development. Just because you're a supply teacher doesn't mean you should stop learning. Attend training courses, read educational journals, and keep up with changes in the curriculum.