I need to learn about how to deal with difficult people...

My past experiences say: 

Having patience is quite important....
Using tact and diplomacy is essential...

Use only a few words so that simple things do not get complicated...

Be outspoken, but sweet at the same time....

Use the principle of 'none is friend, and everyone is a friend'...

Be tough and infinitely rigid, when dealing with the scoundrels, disguised as gentlemen in our society...
Be hard about professionalism and related matters...

Soft and weaker ones are exploited most... and hence not to be weak in any public/social matter... this quality requires a lot of caution, patience and tact....