Keep your writing style simple. Follow the standard rule in all editing: prefer the simpler word to the complex word. This means writing extra or more rather than additional; help rather than assistance; use rather than utilize. Although you might need specialist or technical words, depending on your subject, you should choose the simpler word instead of the more difficult word whenever you can.
Your essay should be interesting but also easy to read. As well as the advice to use the simpler word to the complex word, you can also make your essay read much better if you cut down on heavy words. The traditional advice is to cut down on three-syllable and four-syllable words.
Take this example:
This demonstrates an understanding of the history, diversity and commonality of the peoples of the nation, the reality of human interdependence, the need for global cooperation, and a multicultural perspective.
A more readable style, would be:
This shows we understand why history and common beliefs in each nation matters as across the world, people need to work together and respect their different cultural backgrounds.
Breaking the habit of using heavy-sounding words and replacing them with shorter, everyday words helps make the essay easier to read and encourages you to explain your ideas in more specific terms.