You can probably make a substantial number of writing errors that will go unnoticed by many readers. Two errors that will not go unnoticed are use of an incorrect pronoun as a sentence subject or failure to keep the number correct, i.e., singular or plural. The subject of a sentence is the person, place, or thing you are writing about. You may use the personal pronouns I, he, she, we, and they as the subject or part of the subject.

I am going to a movie. (singular subject / singular verb)

She is going to a movie. (singular subject / singular verb)

He is going to a movie. (singular subject / singular verb)

We are going to a movie. (plural subject / plural verb)

They are going to a movie. (plural subject / plural verb)

Linda and I are going to a movie. (compound subject / plural verb)

She and I are going to a movie. (compound subject / plural verb)

Patricia and Arthur are going to a movie in their automobile. (compound subject; plural verb; plural pronoun)

Do not use the words me, us, or them as a subject or part of a subject. There could be an exception to this guidance if the subject is a proper noun, i.e., the name of a particular toy store.

Ask these questions.

1) Does the sentence I am writing definitely have a subject and a verb?
2) Have I chosen the correct verb tense?
3) If I have used a pronoun in the subject, is it the correct type of pronoun, i.e., nominative case?
4) Are the words that can be either singular or plural appropriately matched? Nouns, pronouns, and verbs can be either singular or plural.
5) Have I used appropriate gender designations?

protect your reputation

1) Use a word only if you know how to spell the word correctly.
2) Use a word only if you know what the word means, i.e., the dictionary definition of the word.

The English language has the word simplify. The word simplify represents an important concept in the advancement of civilization. We gain an understanding of complex problems by breaking down those problems into simple components that we can understand. A mathematician solves a complex mathematical equation by "simplifying" the equation, i.e., reducing the equation to understandable and solvable elements. We do not have the word, complex (ify), in the English vocabulary. Making a problem more complex is counterproductive. Learn to write simple sentences correctly. You will learn to write well. You will communicate effectively.