What Not To Do- Sticky Notes Again

We all want (or should have) our objectives and exemplars posted for the kids to readily see. It's is a good strategy. It helps the kids to know and see what it is they're trying to achieve. But sometimes, is good for the kids to have an example of what not to do. It will help kids to avoid the pitfalls of a lesson. And we know every lesson has at least one pitfall. This is another time  to rely (again) on sticky notes. 

I always try to have an example on display of a student's work (who's moved on, so not to embarrass anyone) that looks pretty good and almost fulfills all the objectives. Where ever there is something that has not fulfilled an objective, I put a blue sticky note next to it. On the sticky note, write what could have been done differently to fulfill the objective.

The kids can go up and look at the art work to see what could have been done differently. Then they can look at their own work and adjust.

Do you have any strategies to help students to avoid a pitfall when teaching a lesson?