In addition to doing things like improving SEO and making signing up or purchasing easy, make sure your homepage looks as perfect as possible.
Consider this: 96% of website visitors aren't ready to buy something. Your homepage is most likely where they'll land. If it's cluttered or hard to navigate, they'll go elsewhere. If the web copy is bad or doesn't show the value of your product/service, they'll be turned off. Sometimes a simple change can boost revenue tremendously.