Power is a means to an end and is based on perception. It is the perception by others that you can bring events to pass that can either assist their case or damage their case.
When the other side believes you to have more specialised skill or knowledge than they do, you have power. They will treat you with respect far beyond the level of your expertise. They also have to believe that you are in a position to make decisions on the spot, rather than having to go back and refer something to your Sales Manager.
The same as you want to negotiate with the decision-maker within the Sales business, customers want to negotiate with the person who is in a position to make decisions. If you believe you have the power - You have it. Confidence levels go a long way to towards perceptions of power. Make the customer feel at ease with your confidence in order to create the perception of the decision bing yours.
