Keep your sentences simple, short and concise. It will prevent mistakes such as writing off topic and grammatical errors like run on sentences.
Many students are capable of writing effective sentences but when their sentences become too long, their sentences lose focus and become awkward to follow.

In addition, avoid using new vocabulary in your assignments or essays. Before you use a new word, make sure you know how to use them in the correct context. Many students pick words from the thesaurus thinking that they can replace words with the same meaning, but they end up using the words inappropriately.