The document provides rules for correctly filling in the verb form in various tenses in English sentences. It discusses the use of verbs in the perfect continuous, future indefinite, future perfect, present indefinite, past indefinite, perfect, and past perfect tenses. Key indicators of tense are mentioned, such as "since", "for", and "by" to signify the perfect continuous tense and "ago" and "last" for the past indefinite tense. The rules cover how the verb form changes based on other elements in the sentence, such as the presence of time expressions or whether the tense started in the past.