Before you speak.
STEP ONE: WRITE DOWN WHAT HAPPENED
Facts, not interpretation.
STEP TWO: DECIDE YOUR OUTCOME
What do you want to be true at the end of this conversation?
STEP THREE: ASK FOR STRUCTURE
"I need to raise [issue] with [who]. Here is what happened. Help me structure this so it is clear and fair."
STEP FOUR: ASK FOR THE OTHER SIDE
"What might they say? What would a reasonable person in their position think?"
Genuinely useful and usually uncomfortable.
STEP FIVE: PREPARE YOUR OPENING
The first two sentences. Those set the tone.
STEP SIX: DECIDE YOUR LIMITS
What you will and will not agree to.
Deciding beforehand prevents conceding under pressure.
STEP SEVEN: HAVE THE CONVERSATION
Do not read from a script. Prepare the substance and speak naturally.
AFTERWARDS
Write down what was agreed, and send it.