What should I take into an account when I want to write an essay about something?

First of all you shouldn't repeat what you are saying multiple times.

Try to do background research and plan out where you are gonna write the different parts of the essay. Remember to have a readable font if you are doing it on a computer and if you are hand writing the essay try to keep your writing neat.

You will get better marks if your essay is at least 1.5 pages long and put in interesting information.

Be descriptive about the specific subject you are performing, so that the reader can understand it well, and can have a perspective of what you're doing, add details, facts, quotes, etc.