Most of what we require students to do in our classes is convergent thinking. One multiple choice answer, one solution to the math problem.
I think it's really important to include versions of divergent thinking as well. Open ended critical thinking activities that will help develop creativity. When researchers measure creativity they use divergent art activities to see how detailed and creative a subject's mind is. I do the same thing with my students. I give them a squiggle or a shape and ask them to turn it into something. In the beginning I get very basic very boring responses, but the more we do these activities the more creative my students get.
Here I gave them just a line:
We do these activities at least twice a month. After the first one I do model some ideas I thought were creative so they know for future activities what I'm looking for.
