Customize your title tags. Each page should have a title unique to that page alone.
Research your keywords thoroughly. You really cannot start optimizing until you have researched out your keywords and know how the optimization will play out.
Use keyword relevant filenames for each web page. If the page is about women's brown boots then your file name should be womens-brown-boots.xxx. Such as: yourdoman.com/womens-brown-boots.html.
Organize your directory structure. Don't throw all your pages into the root folder and don't use too many directories/sub directories. Keep it simple yet organized.
Plan out your internal links. Develop your navigation effectively, implement no follows sparingly, link content to other pages liberally and use absolute links.
Use content effectively. Make sure your content does the job of selling to your visitors but is also keyword rich. Don't go overboard on keyword usage, but only as it functions best for the visitors.
Don't add a bunch of junk links to the bottom of your pages. Footer links are great, but don't just add junk links to pages that serve no value to your visitors strictly for the SEO benefit.
Don't settle for stock content. Take the time to develop custom content for your site. Don't use manufacture descriptions unless you add your own descriptive content as well.
Don't junk up your URLs. Keep your URLs clean and tidy without a lot of excess variables or session IDs.