Sell yourself and your company.
The product is secondary to service because it will only work as good as your company is.
Never badmouth anyone or any product.
Clean and professional appearance. Shave and keep your hair cut.
If you smoke, try to quit. Nobody likes to talk with someone who stinks.
Be honest and solve the customers problems.
If you worry more about the customers needs than your "sale", the business will roll in!
First learn proper grammar and speech patterns. You are judged by your speech and your vocabulary skills. For instance you do sales you sell product using the wrong vernacular and or tense will make you look foolish.
Next do a search for sales techniques I and several others have posted some very good information here.