All customers might have been created equal, but some of them were dropped on their heads when they were very young.  The following represent a few customer types with the more recognisable and common traits that you will have to deal with.  Being able to recognise these traits is really the first step to successfully dealing with these challenging customers.

The Know It All:  The Know-It-Alls are the customers who try to make themselves feel important by making everyone around them feel inadequate or stupid.  Don't be tempted to play one-upmanship with these people or you'll never sell them anything.  The best approach is to be as professional as possible and give them as many compliments as you can.  Doing so makes them feel good about themselves, and then they might buy something.