I often have to take messages but I'm hopeless at it, for me this method works.
Have a messages book by the phone marked out with columns 'for who', when (time date) and message.
My boss knows as soon as I'm engaged in my next task any messages I have taken have been forgotten and comes to look at the book when he comes back to the office or if he is not in the office at end of day. I will put any messages into an email to him. If something is urgent I will call or email him right away. If he is in the office I will put the book on his desk.
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Wisdom must be gathered, it cannot be given.