Like Rocket, I formulate a plan...in my head. I work part-time on the ground so when I do it's never with the same EMT.
Currently we have so many new faces, and even if it's a veteran EMT, they may not be used to my flow. So all I ask is that they "follow my lead".
In my head if we're going to an arrest or some high-acuity call I already know what, and how I want things done overall, so if they follow direction it's usually fairly straightforward. If I give them this elaborate plan, or tell them step by step how to do something, but it's their first high-acuity call it typically won't pan out quite as well.
Displaying a calm, easy-going demeanor will ensure everyone else around says "well heck, the PIC isn't too worried, we're all doing ok." This typically comes with time, hence it isn't hammered on in class.
Two things two instructors taught me that I still implement til this day are:
1. If you find yourself overwhelmed literally step back, breathe easy, regroup, and move forward.
2. (and fire never understands this) If the family is hovering over us while we're working their family member, chances are they are concerned and "want to know" what we are doing. They have every right to know. I will explain it myself as I am doing it if they aren't ushered away by the heroes in the yellow pants. Walking a concerned family member through a traumatic event can be very cathartic to them.
Sadly, this isn't done enough outside of the hospital setting. This too displays a level of collectiveness that comes with time, but will be well worth it when it's done, and done right.