I CONSIDER DRIVING sales one of the most challenging yet interesting professions that exist. This is because one is never quite sure that the things they perceive as good are positive in the actual sense.  Every new potential customer is unique and thus, a completely new challenge. In order to keep the odds in your favor, here are a few tips as to what NOT to do.
Poor Planning
A great number of people go to companies to make sales while they know nothing about the company.  It is important that one is aware of all the company’s undertakings and at least, how they can benefit from your product or service.  Information is plentiful on the Internet and it will likely save you from any embarrassment.
Diarrhea of the Mouth
When one finds a potential customer, people often make the mistake of losing the sale simply by talking too much without giving the potential customer a chance to air their concerns or ask questions. Always offer ample opportunities for the customer to speak.  
No Discernible Purpose
One should always have a purpose.  Be smart; start with the purpose that benefits the client.  For example, helping the client gain more profits.  Take a little time but make the most of it.  Clients might lose interest if you continue wasting their time by not placing your purpose and why you’re there up-front.
Lack of Understanding of the Product/Service
One has to be ready for questions.  This helps the client understand more about the product/service and gain more information.  If you’re new to the company or the product is new to you, take the time to observe the production process and do your best to anticipate tough questions. It’s not that hard to you; if you were the customer, what would you want to know? If you know that you’re going to be faced with tough questions, take the time to develop and rehearse tough questions before you go into the meeting.
Being Too Bold
When I am approached by a sales guy who tries to hit me with an aggressive “in-your-face” attitude, I usually immediately counter it with showing him my just-as-aggressive, “out-the-door” attitude. Being extremely bold or aggressive turns off customers and immediately puts them on the defensive.  They think: This guy wouldn’t have to be so aggressive if he were actually selling a quality product or service. Enthusiasm and passion should be controlled so as to keep you off someone’s nerves.  Study the potential customer and gauge your level of aggressiveness to their personality.
Dropping the Ball on a Follow-Up
Never forget to ask for another appointment.  When one fails to book a second appointment, the prospect may forget about you or lose interest in the product you were selling.  Make time to follow up on prospective clients to show them that you care about them and doing business with their company.
Getting Antsy in the Pantsy About Closing
Hustling to close the deal very quickly can be sales suicide.  In sales that involve several decision makers and large sums of money, the sale agent should be patient.  One should not try to close the deal on the first day.  If you try this, a second appointment could remain a dream.  This is because sales that involve large sums of money require that the client trust you and know you much better.  They almost always also have to like you.  To trust someone takes time and therefore, the client should be allowed to take their time.  Trying to hurrying through a sale could trigger mistrust and subsequent failure of a sale being realized.
Poor Follow-Up
The only thing worse than a complete lack of follow-up is a poor follow-up. Don’t promise what you can’t deliver as this makes the process of following-up very difficult.  Remember to thank the client with a card, a handshake (with eye contact) and the sale details.  Be professional, calm and positive.  Build lasting relationships, solve clients’ problems, and help add value to their business or their life.