I agree with Luckykarma. Don't flinch or show fear in any way. Any animail in the wild senses fear much better than we can. It is built in for their survival. I have had some nasty one over the years, but have been able to mellow most of them out.
What I find intriging as well is that I have gotten chams form people who said they are mean as heck. Yes, the first week, they are like that, but they settle down over time(Some more than others). But 90% of the time , I see improvement.