This is a 1-page sample of a 4-page grammar packet I do every year with my students to eliminate the 18 worst writing errors I see over and over in my years of teaching. We call fixing grammatical errors "slaying grammar demons" to lighten the mood, and it works! You can even spice it up by having students draw pictures of what they think "grammar demons" would look like!
The full lesson takes two days, and my students always say it was one of the most valuable (and fun!) things they learned, and that they still refer back to it years later!