What sheepswitch suggested is perfect. When you start out, you are not going to have any web presence. So start by writing a blog on your website. Then do what sheepswitch suggested, which is to join forums that are related to your niche. If someone is stuck or has questions that you can answer, do not just answer it on the forum. Try to see if you expand that into a blog post. The answer a little bit on the forum, have them visit your site for more info.