1) Write an accessible website
Fully accessible HTML is accessible to both search engine spiders and screen readers. The more accessible you make your pages, the easier it will be for search engines to read and rank your pages.
2) Writing unique content for your website
Unique content is very important. Your website needs to provide content that has different information than what is on other websites.
3) Website Keyword Phrases
Even if you can't get your keywords into your domain name, you can put them into your page URLs. Search engines read the URLs and assign value to the text they find there. So, as an example, if you are selling plastic red cars, you would be very wise to make your pages' URL look like this: www.yourdomain.com/plastic-red-cars.htm
4) Using your keywords correctly and sufficiently in your website
The ratio of your keywords to the rest of the text on your page is called the keyword density. It's important to repeat your keywords in your document, but not too much. Keyword density should be between 3 and 7% for your primary keyword phrase and 1-2% for any secondary keywords or keyword phrases.
5) Make sure you are using your ALT tags
Adding ALT descriptions to your image tags is quick and easy. You don't have to do any complex HTML coding. If you can describe your image or link, then you can add ALT tags to your code. Ideally, your ALT text descriptions should be complete sentences, rather than a list of keywords or an obscure phrase like "company logo small 2." Remember that all visitors are likely to see (or hear) some version of your ALT text so be sure that it's meaningful.
6) Your homepage should contain links to most of the pages of your web site.
If you bury your links, the search engines may not index all of your web pages. Make sure that if you use a Flash or a Javascript menu, that you put a separate menu in <noscript></noscript> tags so that the search engines can read your links.