Always consider your audience
Before you start out writing anything, identify your audience. In the case of product descriptions, that's your customer. Who are they? Teenagers? Moms? Good—now get even more specific. Women, that love vintage fashion? Avid outdoorsmen? Now imagine this person as you write your descriptions. Pretend you are talking to them in a brick and motor store. What words do they use in a normal conversation? Use them. By using the words you'd use in a normal conversation, your descriptions will feel less like marketing.
Answer the question, “What's in it for me?”
So your t-shirts are made out of 100% cotton. That's a great thing to include in your description but go one step further. Why would your customer care about 100% cotton? Well, it's breathable and comfortable to wear in warm weather, plus it's easy to wash and care for. Answer the “so what?” in your product descriptions, so the reader can see more than just the details, but why the details matter to them.
Use specifics, not opinions
Sure, you think your products are the best, top-of-the-line, etc., but your customers know you're trying to sell to them. Don't use opinions, just lead the reader in that direction with specifics. Write down opinions, then translate them into specifics, like this: “Comfortable backpack” = Straps are constructed with a double layer of padding, with three adjustments to find the most comfortable fit for you.
Put the item in their hands
The problem with selling online is that your customer can't see what they are buying. Fight against that negative by putting the product in their hands through description. What texture is the product? Is it heavy or light? What does it smell like? Is it stretchy or firm? If you are stuck, try starting with “Imagine you are…” and concoct a scenario where your reader is using or interacting with your product.
Appeal to the way online visitors read
People do not read a book the same way they read online. Books are read word-for-word, web pages are skimmed through. Keeping that in mind, make your product description easy to skim. Use white space by skipping lines between paragraphs, and keeping paragraphs short and sweet. Use bullet points. If your description is somewhat long, use subheadings, so readers know where to find the answer to a specific question about the product. The key to writing product descriptions that sell is to understand where your online readers are coming from. Identify your audience, then try to answer the “so what?” to show why someone should buy from you. Be specific and allow the reader to imagine what it's like to hold the product, all while making the description easy to glance through. A good product description will have your customers forgetting they've never actually seen what they're buying.
