1. If it is the simple past tense, use was/were.
2. If it is the simple present tense, use am/is/are.
3. If it is the simple future tense, use will.
If it is the present perfect tense, use have/ already.
5. If it is the past perfect tense, use had been.
Extended data:
Usage:
1, be as a verb can be used in the sentence pattern of you/you, meaning "you; Existence ".
Be can also be used with nouns, pronouns, adjectives, adverbs, prepositional phrases, present participles and past participles of verbs, infinitives of verbs or nominal clauses to provide names or information.
Be can also be used in It is/was sentence patterns to describe situations or express ideas, and to indicate time.