Find a successful copy (ads, direct mail letters etc) and copy them by hand. Getting this done over a period of time means you observe the tools and techniques used.... Start a web-based business and learn how to use google Analytics to measure results. Copywriting, as well as its cousins - marketing and user experience design, is all about testing and measuring. You can also go to ad school where you get a chance to team up with an art director. Also, you can refer the book “Ogilvy on Advertising, and Scientific Advertising by Claude Hopkins”. Hope this helps you get started.