Why do self promotion?
You are the world expert on your work. Only you know what drives your practice, what your research is, what makes the things you make interesting. Whether you like it or not, no-one else will ever hear about your work unless you tell them about it.
You already do some self promotion - every time you talk to your friends about your work you are promoting your career, looking for opportunities and building and reinforcing your network.
You can also make your message out your work more effective if you are clear and consistent in what you say - think about who will be seeing or hearing this message and what their principal interest might be; think about what kind of language and jargon this audience will understand - talking to an academic about your practice is very different from talking to members of the public in an exhibition, or people walking past a project you do in the public realm.
Self promotion is not a separate activity unrelated to your work - every exhibition, review or public showing or your projects forms a part of your communication to your audience, and is therefore as individual as your own practice. We can't tell you how to promote your own work - some people may want to use all of the tools and suggestions on this site, while others may feel them inappropriate to their style of working and the kind of artist they feel they are. We offer this guide instead to help you ask questions of yourself rather than provide a fixed and finite set of answers - to find a way of promoting yourself and your work that suits you.
There is a good video by a creative business on self promotion on the Business Link site.