The best way to make sure your own writing is free of bad grammar is to learn the grammar rules for the different parts of the language and how they fit together. 2. Also pay attention to nouns that end on s, but are actually singular. Here are some common categories and examples: Verb tense errors occur when you use the wrong verb. You are one of the most common grammar mistakes. The verb tells the reader your sentences when the plot takes place – in the past, present or future. They must be consistent in the form of the verb, unless there is a reason to switch to another form of tense. Some examples of verb form errors are as follows: Although it is quite easy in English to match your subjects and verbs, there are some common mistakes that people make when the subjects of sentences are pronouns.