This may seem obvious, but it cannot be emphasized enough: You are not selling to an organization or to a conglomerate, but to actual, real people. It is important to remember that all people are different, so you cannot sell the same way to everyone.
Second, no two sales are the same, even if they are made to the same company under similar circumstances.
To become a good salesperson, it isn't enough to know how to sell. You must aim to become a people expert. It may sound shocking, but the best professional salespeople actually like people!
Remember, people buy from people -- they always will.