In an effort to be better at sharing quality basic stuff that works, here’s how I teach quadrilaterals:
I am hesitant to share the files that I use because I’ve borrowed them from all over the interwebs and at this point I don’t even know where to give credit, but here they are!
[10/11/16 update: Most of this came from Elissa Miller. You can find even more awesome geometry resources on her blog.]
I usually start by having students deduce the properties of parallelograms using an old fashioned ruler and protractor. This is because I’ve noticed that students could use the practice. I know there are a lot of quadrilateral discovery activities on Geogebra, but I still think it is occasionally important to practice using different tools.
You can download a editable (word) copy of this sheet here.
After this task, I usually have students complete this checklist measuring, discussing and comparing properties of rhombi, squares, rectangles and parallelograms.
You can download these files: images & checklist here.
After these investigations and discussions, students work in pairs to complete an Always Sometimes & Never discussion of quadrilaterals, described here.
Students also complete the task Complete the quadrilateral developed by Don Steward as described by Fawn Nguyen. This year, I adapted this task into a Desmos activity.
I also include some basic quadrilateral practice, like this assignment. It is just a good, basic, practice that helps expose student conceptions & understanding.