At its basic level, the purpose of the sales presentation is to convince prospects that they would be better off with your product or service than they would be with the money required to buy the product. You are, in effect, asking them to engage in a trade, and you must convince them this trade is a good deal for them.

Here are four factors that influence a prospect’s decision about whether to buy:

Satisfied needs. A prospect always seeks to satisfy the greatest number of unmet needs in the very best way at the lowest possible price. During the sale process, a major part of your job is to demonstrate that prospects will get more of what they want faster by purchasing your product or service than they would if they bought something else.

Credibility. One major factor of influence over a prospect’s decision-making process is credibility. Proof that other people similar to the prospect have purchased a product builds credibility, lowers resistance and increases sales. Every bit of information you can present showing that a prospect’s peers have already wrestled with this buying decision, have decided to purchase and have been happy as a result, moves you closer to making a sale. This is known as “social proof.” We are all influenced by what others have done or are doing. We are much more open to buying a product or service when we know that other people like us have already bought it and are happy with it.

Testimonials. Another factor that influences decision-makers is testimonials. Testimonials of any kind increase desirability and lower price resistance. Testimonial letters or photographs of happy prospects using and enjoying your product or lists of satisfied prospects can be powerful influencers. You should persistently solicit testimonials from your prospects. Acquire them from every source possible and in every form you possibly can. You will find that almost all top salespeople use testimonials that praise and support their product or service and that are relevant to the prospect.

Perception. The higher the level of competence and expertise a prospect perceives you to possess, the more likely he will be persuaded to do the things you want him to do. A person who is highly respected for his or her ability to get results is far more persuasive and influential than a person who does only an average job. The perception that people have of your performance capabilities exerts itself as one of the most important factors that influence how prospects think and feel about you. Sometimes, a reputation for being excellent at what you do can be such a powerful decision-making factor that it alone can make you an extremely persuasive individual in all of your interactions with the people around you. They will accept your advice, be open to your influence and agree with your requests.

If you wish to influence the decision to buy, it is essential that you we aware of these four factors that can powerfully affect the decision-making process.

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Brian Tracy is the CEO of Brian Tracy International, which specializes in business training, and the author of the best-selling Psychology of Achievement. For more information, go to www.briantracy.com.