Best thing to do for a riot is to be nowhere near it.

The second best thing to do is to see a large crowd, sense the potential for unpleasantness, and depart without delay. I strongly encourage everyone to avoid protests of any variety.

If I found myself in a riot that I could not escape, I would try to find a place of cover and concealment, staying out of sight and out of mind as much as possible until it was over or an opportunity to escape presented itself.