For very young students, an activity like "Simon Says" is an effective way to demonstrate verbs. This is a game most students will already know, but explain the rules. You will give them a series of commands, but they should only do the ones you introduce with the phrase "Simon Says...." For example, if you say, "Simon Says stand on one foot," the students must stand on one foot. But if you were to say, "Put your foot down," anyone who does would be "out" and have to skip a few rounds because you didn't start with "Simon Says..." After a few rounds, explain that each of the commands, like "sit," "stand," "hop" or "spin" are verbs because they're something you can do. Explain that if you told them to do something that wasn't a verb, it would not make sense. Give an example, such as "Simon says chair."
For students who are a little older, an activity like charades can help to demonstrate verbs. Write down a number of verbs on small pieces of paper and place them in a bucket or hat. Each student should take a piece of paper and when it is her turn, attempt to act out that verb in front of the class. The class should try to guess what verb each student is acting out.
To help students who already have a strong grasp on the functions of verbs, such as middle or high school students, create projects that focus on writing and that are time-intensive. For example, a writing assignment designed around verbs might give students a limited number of verbs and ask them to craft a story using them. Or you might say, "Write a 500-word story without using any version of the verbs 'to be' or 'to go.'"
Another project for students who are already familiar with verbs and sentence structure is to take a simple work (a children's book, for example), and have students change the verbs. This is an exercise in picking the best verb for the sentence, instead of just an adequate one. For example, if a version of "Little Red Riding Hood" said "She walked through the woods," have students come up with a better verb: did she "stroll," or "amble" or "meander" instead of just walking.