More a point I still have to work on than an actionable note to myself:
Don't get overconfident. It's not enough that somebody is incompetent - you've got to be able to convince people of this seemingly obvious fact. If you can't pinpoint it - just let it go for the moment. Especially if you can't put a number to the incompetence.
As a matter of fact this is something that I've never really gotten around to.
[Explanation of the note for reader who are not myself]
There is a certain kind of incompetent people (e.g. they just have no expertise in the very thing they are doing, they are literally incompetent in such a way that they lack the competences that they need to perform their job) that I still don't know how to handle - those that don't know the details of the job their doing but are yet well versed in easily graspable abstractions of the work they should be doing.
The only way to handle these people - who sometimes have a real bad effect on the morale of whole teams - seems to be a very detailed breakdown of their shortcoming. But that on the other hand leaves me in the position of a nitpicker [erbsenzähler] who wastes everybodys time - including my own - by going through seemingly unimportant details.
Of course - applying the rule of three - that can't be the only solution - but although I've been trying for years I haven't been able to find any other angles. At leas not up until now - still trying!