If you are a full stack web developer, and you deal directly with businesses, these are some tips that may help you, these are based on my own observations and on my experience as a freelancer and a full stack web developer:

1- if you are dealing directly with the client, take some sales courses online or simply check YouTube to learn more about sales and how to deal with clients.

2- improve your listening/communication skills and try to understand the client’s business and problems, this is an important skill in order to build the right product and to suggest the correct solution for the problem.

3- if you want to focus on the full-stack then pay attention to your front-end skills, mainly CSS and similar skills, since clients care so much about the UI, and even if you have a great back-end code they probably won’t care at all if UI is bad, so focus on this part and don’t ignore it.

4- keep improving your skills in general, and focus on a specific stack and master it and keep learning and improving.