Why are you asking this on an electronic forum.
May be because he realises that there are many here on ETO who rely on good communications in their day to day work and are willing to give advice.
Are there any books which can recommend?
There is a book called "Eats Shoots and Leaves", I have never looked at it but I think it may help.
What can I do to make myself a good communicator?
Don't use "textspeak" in any written communication.
When speaking:
Think what you are going to say before you say it.
Do not mumble and mutter.
Speak slowly and clearly.
Speak in the standard language (English?) appropriate to the location.
Do not use local dialect if the listener does not understand it.
When speaking to someone, look at them, do they look like they are understanding what you are saying?
Generally:
Does the listener/reader know the background to what you are telling them?
If not, ensure that there is enough information to put what you are saying into context.
Read through written communications checking for typing errors and ambiguities.
If time allows, when you have finished writing something take a quick break before reading it, does it still make sense?
Just a few ideas, based on years of experience.
JimB