Speak to your customers in a language they can understand. An excellent resource for helping you to do this as you start out on your copywriting journey is Reddit, where you can find millions of threads written by people from all walks of life. It's a great place to find out what makes different types of customers tick, and why, from working professionals, to stay at home parents, to students, and retirees.
You can go really niche, finding special interest forums on everything from rock music to pets, so you can see how people with an interest in these subjects really think, talk, and speak. Amazon Reviews can also help you understand your target market's needs. By observing how customers describe products they love and noting what they don't like, you can angle your copy to hit their pain points and outline the solutions they require.
The best thing of all about Amazon reviews is that they show you how customers actually talk about products. It's smart to implement this approach in your copy so you can then connect with people in a language they will understand.
So, go on Amazon, look up the products in your niche and see what others are saying. See what brands that perform well are doing right and see what brands that receive bad reviews aren't doing. This is truly invaluable market research that you can conduct right now, from your computer or smart phone and it will help you greatly as you'll then know how to write for your market.