I made a simple worksheet asking students to use graphing calculators to graph quadratic equations in sets of 4. For example, the first set was:
They were then required to sketch the graphs and write a statement about how the graphs were related by transformation.
The final part of the lesson was when I really stretched them. I created a powerpoint with images of graphs I had made using an online graphing calculator and asked students to make their calculator screens match my screen. Without having formalized rules for quadratic equations and graphs my students were able to do it, they discovered the rules and patterns.