For me, training or not, first shots are ALWAYS double tap, center mass, on closest or main threat. While not strictly necessary, yelling, "Stop, drop your weapon" is a GREAT idea in that you never know who is hearing/witnessing, or even taping the acts in question.
The earlier suggestion about shooting on the move, while seeking cover, is also a great one imo.
There really is no other "advice" other than shoot to stop the threat imo. Life and the scenarios of self defense, particularly with handguns, is so varied that this is usually sufficient directions.
And one final thought, practice failure drills, even with wheelguns. If it can go wrong, it will.
Just my .02.
Tim