No. 1: Have a good attitude
The reality of work is that attitude matters. Some people may respect the skilled person with the strong or difficult personality. However, they will not necessarily enjoy working with him on a daily basis.
People have enough drama in their lives and they do not necessarily want to deal with co-workers who regularly create conflict or tense work situations.
While it may be difficult to manufacture a "nice" personality, that doesn't mean that people shouldn't try.
If a company is trying to decide between two people of equal skills and vocational worth, chances are they are going to make a gut decision based on personality.
Therefore, you should do your best to have a positive attitude so that you can build quality relationships with other people and continue to be perceived as a valuable asset in the organization.