Faith is a step beyond belief. Faith is belief and hope compounded together and increased. When a person believes something they may or may not do something about it. While faith is a positive power, it is not simply positive thinking.
When a person has faith they will act on the belief that is present in their mind. That is why faith is a saving power. Not because in and of itself it saves but because when a person has faith in God and Christ they will follow the divine instructions given by them. There are many examples of faith in the scriptures that indicate that power flows from it.
Power flows when an individual or group takes action and that action is blessed by the powers of heaven. The most important facet of our faith in God is that it produces actions that invoke the saving powers of Jesus Christ into our life and a willingness to follow his example.
There are also examples of belief that show that no power comes from simply acknowledging a fact. Increasing faith, and faith to perform miracles is a gift of the spirit given to those that covenant with God to follow in their own life and serve him in ministering to His sons and daughters. Faith in the first instance is something we develop by exercising our agency or free will. Increasing it on a constant basis is also our choice but is boosted through mercy and gifts of the spirit and our willingness to obey God.
Faith comes about by evidence of some principle or fact. It can be true or false. Acting according to the evidence and seeing the result one can gain an increase in faith and prove the true or false nature of the evidence. The scriptures are evidence of God's dealings with mankind. They are the primary evidence for faith in Him and of his existence and power. Doing what is contained in them is the result of our faith and continuing to study them will increase our faith.
One can only gain true faith in God by having a correct understanding of his character and attributes. Thus the statement in John 17 "And this is life eternal that they might know thee the only true God and Jesus Christ whom thou hast sent." Any false notions or incorrect reasonings about who or what God is will reduce a persons opportunity to develop the full measure of faith that is available to us.