First off, I prevent by checking the equipment's condition, the rigging, and I talk about the session objectives and procedures: what we'll do, how, what happens if, etc. If the handler is inexperienced, I get an experienced person on the lead as well, while I decoy. I already have my communication down pat with three guys here, regardless of whether I'm the decoy or they are.
With working dogs, if the lead, harness, muzzle, collar is not up to it, or was forgotten, that dog does not get worked that day...and an action report is filed on the handler. This almost never happens here.
The rigging...everything must be properly fitted, with redundancy where applicable. I don't feed sleeves so, on a suit...no big problems. But during civil agitation, a problem can get big in a hurry. I carry a tug in my pocket, and pre think about escape routes and other items available near the work area. One important tip here is that when you clip on a lead to a harness, the open side of the latch should always face up. That way if something happens to the latch, gravity and position are still acting on your behalf.
Finally, regarding inexperienced handlers...and in my case show dogs...the handlers are too fidgety, too loud, too static, or all (and more) of the above...so I have them next to someone with a bunch of experience, loosely participating, and hopefully learning.
One more tip ... is some dogs get blood supply to the brain reduced if they are on improper equipment and/or allowed to strain too much against the equipment. The handler must be careful here...if the dog falls or semi faints, because the handler could get inadvertently bitten.