Form the past tense of the verb by adding "ed," or the past participle by adding "have," "has" or "had" and then "ed." If this is possible, the verb is a regular verb. For example, "the boy walked to the store." Or, "the boy has walked to the store." This means the verb "walk" is a regular verb.
Form the present participle of the verb by adding "ing"." If the verb does not change, it is a regular verb. For example, "I walk" (present) is changed to "I am walking (present participle)." The same is true when changing it to the past participle, which means including helping verbs like "was" or "had" before the word along with "ing." For example, "I was walking (present participle)." An irregular verb such as shake cannot be changed to the past participle without changing the verb. "I am shaking." becomes "I shook."
Look up the verb in the dictionary if you are uncertain that you've made a proper word by adding "ed" or "s," or if you are still not sure the verb is regular or irregular. Irregular verbs do not follow a pattern like regular verbs and this is often noted in the dictionary. For example, the irregular verb "shake" is listed in Webster's with "shook" and "shaken" noted in brackets as other forms of the verb. Other irregular verbs like see, do and am also have their alternate forms (saw/seen, does, are) listed with their definitions. Regular verbs such as walk, lift, and laugh are listed in the dictionary without notation because their forms are not altered when changed to past tense.