Always, but always, concentrate on the benefits of your offer rather than the features. However, exciting or impressive you may find the features of your offer, remember that the readers want to know whats in it for them - in other words how will it benefit them.
Only write about the features if they enhance the value of the benefits in some way. Copywriting is not as difficult as some people try to make out, but it does require thought and research to really engage with your potential customers.
First of all, you are not writing a novel. I love the work of Charles Dickens but he would have made a lousy copywriter! All copywriting needs to be pithy and to the point. Avoid flowery language and lengthy explanations. Remember, your reader will usually have a very specific idea of what he or she is looking for and will be asking the question when faced with any copy: "Whats in it for me?" Always try to anticipate any particular questions your readers may wish to ask and answer those questions in your writing - before they ask them. Think from your potential customers standpoint all the time. Unless you have a particular experience you feel you need to share to reinforce the information you are discussing, keep the words, "I", "Me" and "My" out of your writing. "You" and "Your" are the words to use; this is not because your readers are selfish, but because they are looking for something very specific to fit their own particular needs.
I am not going to try to give a comprehensive review of the whole copywriting gamut within this one article, there is neither the time nor the space. However, here are a few bits of advice which are well worth considering when you come to write.
Copywriting is one of the key skills in running an online business. Communication in any form of business is a critical issue. A shop owner will come face to face with his or her customers on their shop premises. Someone based in an office or workshop will often encounter their customers face to face or possibly by phone. Service engineers dealing with household problems will meet their customers in their own homes when calling to make a repair, to service equipment or install new components. Internet marketers will probably never meet their customers face to face nor hold phone conversations with them; their only form of communication will be the words on their websites, in emails, articles or sales letters. Without the skill to use those words in the right way, running an online business is going to be very difficult and, probably, unprofitable.