Grammar and usage carry high stakes in writing and speaking: errors or departures from convention can have a serious impact on a writer's clarity and/or credibility. This is particularly true in academic settings. These resources should put you on the right path.
Top 20 Errors in Undergraduate Writing
Readers judge your writing by your control of certain conventions, which may change depending on your audience, purpose, and context for the writing. Use this helpful list to avoid errors.See The Top 20