Belief is the acknowledgment of an understanding about what you are focusing on. Belief is the result of confidence. Once you have the belief then you have a specific understanding. This however has also another side in that your belief can be manipulated into the wrong direction if you are fed information that restricts that belief.
Limited belief is the hardest one to identify as it also clouds the subject in a false sense of reality and is quite often hard to convince otherwise that t has the wrong end of the stick. There are 2 sides to belief. One good and one bad. One negative or shadow effect belief and one pure and precise positive and strong.
If you wish to really have a strong belief then find out first why you do not have it then find out how you can obtain more knowledge to correct the situation so that your belief can be more absolute. This of course again can be difficult if you do not have the correct guide/teacher to lead you in the correct direction and supply the correct knowledge.
Manipulation of belief is also the manipulation of ones free will. This is not smart as it will come back on the person manipulating that free will so it is a no win scenario.
To believe in a product for instance that you are attempting to sell you should not only just sell the product but also use the product yourself. This using will help to strengthen your belief in what you are doing as you will obtain personal results from the usage.
This is smart and will lead to success!!