Use am/is/are 1) with adjectives: He is helpful. 2) with nouns: He is a pilot. 3) with progressive verb forms: He is working on his project. Use do/does/did with a main verb in its base form (dictionary form) to make a sentence negative or to ask a question. She doesn't work in a store. Does she work in a store? Where does she work? Also, use do/does/did when it is the only verb in the sentence to mean "make". I do my homework. Don't use do/does/did with adjectives: No! He does happy. Yes! He is happy. Don't use do/does/did with -ing verbs (progressive forms). No! He does visiting his parents. Yes! He is visiting his parents.