Generally speaking swarms are going to be docile but...
That swarm you are about to shake could have been down the street yesterday and had kids throw rocks at it, dislodged, went two hundred yards to be sprayed with a water hose by some lil grandmother!
You just never know what you gonna get, so...
Keep a bottle of sugar water with you at all times, this has calmed many a swarm that appeared agitated and quite possibly hungry.
I like to test their temperament with an open palm. If they begin shaking from side to side as if agitated (which they probably are) I lightly spray them with feed and give them several minutes to calm down. I then again do the open hand touch.
Sometimes you still get stung but that just goes with the territory! :-D