Know your stuff. If you have a thorough understanding of the product, your competitors and the market, your confidence will show and closing a sale will be much easier. You don't have to be a lecturer or tell everything you know, but being in control of the facts can make a big difference in your presentation and the way it's received.
Check for signs of rapport. Interacting successfully with a potential customer is all about making a connection. It's part personality and part appearing competent and knowledgeable. If you've been able to establish a rapport, you'll feel it. The customer will be asking questions and treating you like a consultant. He may be taking notes or showing more relaxed body language. Your counsel should have value in the exchange. If you feel that it does, your close is much more likely to be successful.
Build a relationship. After establishing a rapport, you can make the exchange more personal by showing a little of your personality, telling a joke, mentioning an anecdote about your family or suggesting in some other way that there's a human being behind the product. It shouldn't be intimate, but it should be something that personalizes the exchange. At the close, use first names if you can, and be friendly. It's easier to buy from someone you like than from a stranger.
Learn the details. Getting the customer to open up about his needs is one of the big keys to success. Listen carefully, and remember what you've heard. At the close of the exchange, you should be able to recite all of the details that helped you determine the right product for him. If you can't, you still have work to do.
Ask for the order. Even if a customer doesn't look like he's interested in buying your product today, ask for the order anyway. This is an effective method of opening another avenue for communication. If the customer has objections, you many never know what they are unless you get him to talk. Refusing your request for an order will get him to reveal what he's thinking and what his objections may be. Once you know more, you can change your strategy or finish the exchange.