English grammar

I'm looking for help with English grammar, specifically with regards to subject-verb agreement. I need help learning the rules, not necessarily editing existing content, so I'm looking for someone who can provide me with written explanations that can help me understand the subject matter better. I'm open to suggestions on the best methods for the delivery of such material, though my preference is for written explanations. Ideally, I'm seeking someone who can help me learn and understand the material in a comprehensive way, helping me to make use of it in any future writing assignments I may have.