How do I prevent chalk pastel from getting smudged?
Once you've finished your work, if you need to protect it from being smudged, use Fixative Spray that is made for specifically this purpose. Hairspray will also work in a pinch.

Only do this once you're finished though - since it will make it near impossible to add more chalk once it's done. If you need to transport unfinished work, do so in a tight folder, with another blank piece of paper placed carefully over the top of your work (with a bit of masking tape around the edges for extra security).