OF:
It determines a link between a part of something to its whole. It is the most frequent used preposition in English.
Example:
She is a girl of 18.
Some parts of her body were swelled up.
Most of the people are gone.
The plays of Shakespeare are worth reading.
ABOUT:
It is used to refer something that is on the subject or concerning something or someone. It is a simple way of saying approximately.
Example:
I was about to hit a truck.
She cares too much about him.
I have about 30 chocolates in my bag.
This blog is all about computers.
FOR:
It means that with the object or purpose of something. It highlights a suiting of purpose for something or someone.
Example:
I will change for you
I have something beneficial for you
Apple is good for health
I kept an extra spoon for you.
WITH:
It means that it is accompanied by something or someone.
Example:
I came with Alex
I brought an extra can with me
He is fighting with his cousins
Candy is free with the chocolate.
BY:
By refers to as something is linked to something or someone. This specific preposition is mostly used in a passive form.
Example:
Do you travel by plane?
It was done by me
I wrote this by myself.