There is nothing mystical about SEO, it is a matter of plain common sense, although many so called gurus will attempt to confuse the issue talking about Google Panda updates and black hat methods of trying to beat the Google algorithms.
SEO start with the basics of finding a niche market and researching the relevant keywords. Then you purchase a domain containing your main keyword.
The next stage is important you need to build a website or blog paying attention to title, metatags and content. Content is king and you will need to provide fresh content on a daily basis.
Once you have your website complete, submit it to Google and then start building backlinks. Your back links need to come from sites which have contents relevant to your keywords and the links need to contain your main keywords.
The method I use is to build 500 one page web sites and place 1,000 classified adverts each containing more information about my chosen niche. now once the initial target is reached, I actually continue adding new web sites and ads on a daily basis.
You also need to write Press releases whenever to have something to share about your business.
You can build further links by creating blogs all leading back to your main site or blog, overtime you will see your Alexa ranking reduce and your Google search results improve.
To be honest I do not recommend blog commenting except where the blog is about your niche and remember when you are posting comments in blogs on forums you need to supply good content. Far too many people tend to post frivolous comments just to promote their signature link, this is BAD practice and will often get you banned as a spammer.