Think about it, why would a retailer buy your item? Because they want to sell it to their buyer; the end consumer. Therefore, the most important part of your job is to help them visualize how the end consumer will perceive the value of your item. Help them visualize this and they will be much more likely to purchase your item.
The first step to doing this is to consider the type of retailer your buyer is representing. A buyer working for a retail store will have very different needs than a buyer for an electronic retailer like a shopping channel, internet company or direct TV business.
The buyer for a retail store needs an item that 1) looks good on a shelf and 2) is easily understood by the consumer. The first need would be addressed by product packaging experts and the buyer knows right away if it has shelf appeal or not. The latter, on the other hand, is where your sales presentation will make all the difference in securing a purchase order.
If the item you are selling is similar to many items already on their shelves, has been on the market for a long time or has already proven itself as a good seller, your buyer is probably already interested in the item and all you have to do is meet their profit margin needs, beat your competitors price and/or maybe throw in a little advertising money.
But...if your item is new to the marketplace or is more expensive than items that look similar, you had better convince them that their customer will understand what it is, why it's a better mousetrap and why they want to buy it! That means you need to help your buyer understand how their customers will see it.
For example, if you are selling to an electronic retailer you should go to the meeting with a list of live demonstration ideas. You will want to tell the buyer, "we can show how this blender will grind a brick and then dice tomatoes!" or "this oven will cook biscuits in 3 minutes, right before the viewers eyes!".
If you go in to a buyers meeting and say, "here's my blender and it works great" or "look at my oven, it cooks faster"...get in line behind all of the other blender and oven vendors! You need to help them "see" your product as their customer will "see" your product. If you can do that, it will go along way to helping you get the order.
If you are meeting with a brick and mortar buyer and the buyer doesn't "get" why your item is better than the others already on the shelf or doesn't "see" why their customer would want it, you should be prepared "show" them more. You should have a live demonstration of the product available for them to view on your laptop. Let them see the item in action. That will help you get the sale but won't help them to get the sale from the end customer. Be prepared for returns and forget about reorders!
You should be poised to offer sales aides. You may need to provide the retailer with a TV pre-programmed with a video showing the product demonstration or even offer to provide live in-store demonstrations. Since those offers require money it would behoove you to have the costs pre-calculated into your offering price.
Bottom line: Prepare your presentation and product cost by keeping this objective in mind: Sell to your buyer by showing him how you will help him to sell to his buyer!