The age of your website
For Google, a website’s age is a very relevant factor.

Broken links and grammar mistakes

Google doesn’t like to send traffic to websites that have broken links or misspelled words.
Frequency of updates
If Google and Yahoo see that you update your website frequently they are more likely to rank you higher.
Having a sitemap is a great idea because all your pages and their links will be listed there.
External links quality
If your website links out to low-quality sites, it will affect your rankings in a negative way.

Valid HTML

Validate all your pages using
Text content
Have your content in plain text, not in an image or Flash animation.
Site architecture
Make all your links accessible from the home page or second or third level pages at the most. If in order to find blue Nike sneakers you need to go to the home page, then click on “clothing”, then “shoes”, then “Nike”, and finally “blue”, that is too many clicks. The deeper a page is buried, the less important Google assumes it is.
Breadcrumbs are excellent for navigation and also help with search engine rankings. If you don’t know what breadcrumbs are, this is an example: You Are Here: Home > Clothing > Shoes > Nike.
Have explanatory text links
If you are going to link to the shoes section you should have a link that says “Shoes”. If you prefer to use an image, make sure its alt tag says “Shoes”. That way, search engines can figure out what each link points to.
Add new pages frequently
Google and Yahoo love websites that add new content frequently.
Make sure that your server is fast and never down
Be very careful when you choose a company to host your website. If their server is down frequently, not only will your visitors miss your website, but the search engines will not index it either.
Sign up with Google Webmaster Central
This is the best and fastest way to submit your website to the search engines.
Tomorrow I will talk about the most important thing of SEO, link building. Getting quality links can get you at the top of the search engines in record time.