I sat down some time ago and tried to give a tight definition of what it means to be one who builds up rather than one who gossips or tears down. Here is what I came up with:
Definition: Someone who believes the best about another, will seek to obtain multiple sides of a story before drawing conclusions, and seeks at all times to avoid situations where his or her words will damage the reputation or break the trust of another.
In this life, you cannot avoid talking about others, but you can control what you say.