There is a methodology also.
Know your laws for your area
Deflect questions calmly with questions ("Am I required to answer that, officer?", "May I wait until I see an EMT/go to the hospital?" (in the case of a shooting)
Have a lawyer on speed dial (IOW be efficient, be confident and practiced)
Do not touch your firearm even if told to hand it to the officer. Say 'I respectfully decline to touch my firearm'
Don't just say 'nothing', but inform the officer "I'm going to wait, my lawyer told me not to talk. Am I required to answer that? Why am I being detained".
If he says 'do you know why I stopped you', do NOT say a reason. Say 'why did you stop me, officer?'
But as to any facts of the case, nothing you say will ever help your case, so don't start painting yourself into a corner. Even innocent comments other than "I was in fear for my life, I need to see a doctor" could be held against you.
Especially don't say 'I shot him. Say 'send an ambulance, someone is injured'. If you can, during the incident have 911 on the phone and put the phone where it will register you say 'stop, go away, I don't want any trouble', and things of that nature.
You might even go so far as to compile your thoughts onto a card that you could read and which has your attorney's name and phone. Have your atty review what you might say if you want to be rigorous about it.
IMO, just as we should practice and rehearse scenarios, we would be remiss to omit rehearsing and practicing the aftermath when you will need help staying cool.