No secret - just plain old dumb luck. My first batch (the Dark-n-Scary) had just as much head as this one, but I have just been following the recipes. Might be my well water chemisty has something to do with it - haven't gotten it analyzed yet so who knows. For carb, I just hooked it up at about 12 psi and left it for about 10 days in my pantry.
It holds that head for few minutes, then starts to settle. I have also ben serving it at my pantry room temp - haven't hooked up the chest freezer yet - mid 50's.