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.
After these investigations and discussions, students work in pairs to complete an Always Sometimes & Never discussion of quadrilaterals, described here.
I also include some basic quadrilateral practice, like this assignment. It is just a good, basic, practice that helps expose student conceptions & understanding.