1. Keyword research
What - Develop a list of keywords used by people who would buy what you're selling.
How - Use the Google free keyword tool or something like
Market Samurai which uses the Google data.
Why - So your site attracts people who are looking for what you're offering
Warning - Don't chase difficult phrases that you can't rank for. Check the strength of the competition (Market Samurai will help here).
2. Optimise your site's pages
What - Make sure you are putting keywords into your page title element, meta description and header elements (H1, H2 etc).
How - Depends how your website is built. If it's static then edit these elements for each page.
Why - Because search engines use these elements to 'understand' what your page is about.
Warning - Don't stuff these key elements with keywords, write for people, using keywords, not for search engines. Don't chase all your important key phrases on every page.
3. Build links to your site
What - Search engines view links as votes. Votes for your page make it more important in the eyes of the engines.
How - Good content will attract links. Article marketing can help. Ethical blog commenting can help. Asking for links from other relevant pages can help.
Warning - Link building is hard. Rubbish sites won't attract links and will rely on link spam. Google work hard to stop link spam from being effective (not very well but they are trying).
Now there's a ton more stuff to think (and worry) about but if you nail these basics and keep doing it you won't go far wrong.
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