Design and content guidelines of Google

• Make sure that your site is made with a clear hierarchy and text links. Each and every page should be approachable from at least one static text link.
• It's advisable to Offer a site map to your visitors with links that indicate to the important parts of your site. If the site map is bigger than 100 or so links, you probably want to break the site map into separate pages.
• Your content should be informative and should be updated. It should provide all the desired information of the Visitor.
• Take care of the meta key-words or rather about the words that users would type to find your pages, and make sure that your site actually includes those words within it.
• If you have any important name or content or links that you want to display in your site then try to use the text instead of the images. Because google crawler can not crawl the text contained in the images.
• Use descriptive and accurate (title) elements and alt attributes.
• Look into the broken links and correct HTML.
• If you want to use dynamic pages (i.e., the URL contains a "?" character), be careful that not every SE(search engine) spider crawls dynamic pages as well as static pages. It helps to keep the parameters short and the number of them few.
• Do not add more than 100 links in a page. Otherwise it will be assumed as link farm.