Make it relevant to behavior, not personality..'when you did'..or 'when you said'....I felt..
Acknowledge what is going right, as well as what needs improvement. A little praise goes a long way.
Listen to the other persons point of view, and let them know you have, be open to their feedback too.
Be trustworthy: don't gossip or talk to others about the issue if they are not involved.
Ask for suggestions about how how to improve the situation going forward.
