I got to all of these things.
I do keep my wits about me (well...), I think it is smart to know where the fire exists are in a theatre, if you know what I mean.
If things start getting rowdy...which they never have...I will just ease into a nearby coffee shop and order a latte.
One thing I do think about is passing through police barricades. If they are thinking of kettling, then they will establish a parameter (sp?), so once you are inside of that....and if trouble starts....you may get sort of lumped in with the a-holes breaking windows and swinging on the War memorial.
So if I were to see a police barricade/checkpoint, which I never have, I would just pop into a coffee shop and get a latte.