Ask students what they already know about participles and parts of speech. If necessary, review these fundamental concepts. See if they can recall past participles and present participles. They will also need to know about nouns, pronouns and adjectives at the very least to understand the function of a participial phrase.
Write the following sentence out for students to see: I saw the boy running to school. Ask a student to identify the participle, which is the word running. Point out the word school and identify it as the object of the preposition. Now write out several sentences, some with participial phrases and some without. Ask students to determine where the participial phrases are located.
Write the following sentence out for students to see: The class was getting out of control. After a student identifies the word "getting" as the participle, point out that there is no object. In this case the prepositional phrase "out of control" completes the participial phrase. Ask students to come up with other such examples.
Demonstrate other ways to create participial phrases with phrases such as "broken dishwasher," "repeating video" and more complicated examples such as "sought yesterday for questioning." Help students invent their own phrases in writing.
Finish the lesson by asking each student a question about participle phrases. Ask about the principles involved. If a student does not know the answer, tell him that you will come back to him with another question after you have finished with the other students. If you exhaust those possibilities before all students have answered a question, ask students to either identify participial phrases verbally or say one of their own to demonstrate understanding.