Dealing with people

Dealing with people is probably the biggest problem you face, especially if you are in business.

[...] even in such technical lines as engineering, about 15 percent of one's financial success is due to one's technical knowledge and about 85 percent is due to skill in human engineering – to personality and the ability to lead people.

One can for example, hire mere technical ability in engineering, accountancy, architecture or any other profession at nominal salaries. 

But the person who has technical knowledge plus the ability to express ideas, to assume leadership, and to arouse enthusiasm among people – that person is headed for higher earning power.

If you teach a man anything, he will never learn.

Bernard Shaw

Reference:
How to Win Friends and Influence People by Dale Carnegie