There were few points I kept in mind while writing an essay, Those were:

1. Understand the topic: the first and most important step is to understand the topic, you have to focus on what is being asked, for example, if topic is "women emancipation" you can't simply put everything you prepared in the essay "women rights" you have to filter that information, and write stuff only related to the topic.essay writing is just like "peeling an onion" you have to remove layer after layer to reach the core.

2. outline as a "miniature" of your essay : it should be brief enough to keep interest while comprehensive enough to cover the subject in question.

3.consistency/ flow of ideas: one point/idea should sync in the next point smoothly. The examiner should not feel the jerk of shifting from one idea to another.

4.simple and grammatically correct English : don't use "Heavy vocabulary" just for the sake of showing it off. Use the words which best describe the idea, no matter how cliche they are.

5. graphs and illustrations:: (if neccessary) if you are running short of ideas or time or space while writing an essay, graphs and charts could come handy in the situation, saving your time while delivering your point effectively.
i hope it helped.
regards,