The first step in SEO optimization of a site
What is the first thing you should do in SEO. No doubt this is a careful selection of keywords for each page of the site.
Make a list of all pages within your site. Consider what would have be searched for by users who will want to visit each page. Do research on the Internet, what word or phrase from those is appropriate for each web page. Use free online tools for this purpose (such as Google Keyword Tool).
Once you see what are the most searched phrases, select yours (for example two for a page). These will be your keywords. This is the beginning of your SEO.
You can explore what is the competition for those words. Search for your keywords in Google and see what sites are ranked on the first page. They will be your competition. See where they get links and what PR they have. Use online tools.