What is the best way for a sales person to approach you ? to sell his company product or service ?

When buying something , People consider the opinion of their reference groups ( friends , family members , colleagues etc ) so never try the "cold calling " . Ask to be endorsed to every customer who bought your product . When I was a sales person years ago , I had set an endorsement objective to myself . After selling the product , I was asking at least5 references to the customer who bought the product . It is the same with corporate sales  too . Work always with warm references .  Sell the product to a well known businessman or celebrity and ask his/her permission the use his /her name during future sales negotiations . Ask written testimonial messages / letters to old customers and send them to potential customer . Always push the marketing department to support your  sales with national /international campaigns , marketing events , advergames , award programs , loyalty programs . Prepare personalized negotiation offers and messages for potential customers and make them feel "special" . And finally know very well where to hunt . 

This is a good question and the answer is already embedded in my sales mastery class that I give to my clients .

In my view, if you are doing "push" selling for a product/service (X)  from your company (Y) ,,, then the following is necessary to close the sale if the sales person manages to answer these questions successfully

1. Who are you and who do you represent ?
2. Who is this company (if it is unknown) ?
3. What is this product/service that you are selling ?
4. What is its benefit to me ??  Why should I consider buying it ?  
5. Isn't there a better "similar" product/service in the market that I should consider ?
6. How much do I need to invest in buying this product specifically ??  and how does it compare to competition ?
7. What other things do I need to consider when buying this product/service to be able to fully benefit from it ?
8. Why do I need to buy this product/service specifically and not other similar/comparable ones ?
9. Why should I buy this product/service from this company (reseller) and not others ?
10. Why should I buy this product/service from you personally and not from others in your company ?

Now, depending on the product, the company, the customer, the sales person and the specifics of the situation, additional points may be necessary to add.  Hope this is of help to you !!