Jakob Nielsen's 10 general principles for interaction design. They are called "heuristics" because they are broad rules of thumb and not specific usability guidelines.
Before you go hire a business coach or sales person, enrol in an online course, follow a get rich quick scheme, do this first. Warning, this is a long list of things to do. No easy answers, no quick fixes, but the bare minimum of what you need to do before looking for more help. Remember, people hire who they know, who they like and who they trust. So time to get known.
Small Biz, Biz Dev
How to Get More Clients — The Futur
Knowledge
Why Web Accessibility Is Important and How You Can Accomplish It