The advice I give to all my colleagues (and family) is this: you can’t control the behaviours of others, which means situations can go to places you were not expecting. So for me rule number one is to write everything down. Dates and times and any incidents or interactions that you’ve had. All communication with the other person through official channels and if you need to speak either do it with witnesses, and I know sometimes that’s not possible, so write everything that’s said between you down. If you can do it while you’re meeting with them great, otherwise straight afterwards. Sounds like a lot of work, and it is, but depending on what happens in the future it can save you a lot of heart ache

I don’t think it’s the best but in such cases, I personally take the minimalist approach.

Keep all communications on official channels, and only send precise and to-the-point messages with as much brevity as possible (of course, make sure that your points are clear and that you are responding to their main queries as well). Make it as if they’re talking to an intelligent robot.