In applying to universities, many students will focus on their grades, but have often neglected the importance of the essay, which is a determining factor for your acceptance. I would recommend you to start early, give yourself sufficient time – at least a month or two for preparing the essay. You should compose at least 4-5 drafts on each essay, especially for your targeted schools.
The words on your essay is very limited, often times you have to deliver your points in about 300-400 words. Therefore you must go straight to the point and be clear and concise.
I used my work experience for my Queen’s PSE. The point of the essay is to differentiate yourself, therefore avoid topics that do not serve this purpose. For example, just stating that you have a part time job and your role is not sufficient. Instead, you should state particular instances or situations as evidence to demonstrate your leadership or problem solving skills, or how you take initiatives. There are certainly instances where events do not evolve as planned. What have you done to handle the situation? What value have you added to your team? The answers to these could be valuable topics to write about.