1. The first source is the environment.
“Few people are capable of expressing with equanimity opinions which differ from the prejudices of their social environment. Most people are even incapable of forming such opinions.”
2. Events, small or large, can help foster beliefs.
3. A third way to foster belief is through knowledge.
Knowledge is one of the great ways to break the shackles of a limiting environment.
“I was enriched by my attachment to him; the level of my expectations was raised by his example.” -Jackie Robinson
4. A fourth way that results are created is through our past results.
............
5. The fifth way to establish beliefs is through the creating in your mind of the experience you desire in the future as if it were here now.
6. Experiencing results in advance.
From "Unlimited Power" by Tony Robbins