It's good that you want to become silent. I like this thought of yours.
But instead I would suggest you to become ambivert, means introvert from inside and extrovert from outside. In short maintain your inner peace and while speaking, speak with confidence.
Now comes the next question. How to attain that inner peace? If you attain inner peace, no need to work on your communication skills as latter is dependent on former.
As usual and you would be knowing this, 5 minutes of sitting in “Dhyan” is good at initial level. I also practice this. Later on when you grow in this direction, start practicing the same under some Guru as this will take you in the right direction ( Decide this on your own whether to take guidance or not as till that time you would be wise enough to take your decisions)
And one simple but complex formula I would give you is
Start helping others and don't expect anything in return. ( Help can be in non-monetory form also).
I think this formula need not be explained. It all comes thru experience.