Good design makes for a visible website. It is always a good idea to:
- Use a Textual Menu system (instead of images which look nice but Google cannot see as well)
- Offer a sitemap to important parts of your website (categories)
- Keep list of links reasonable (so you do not drown out important links)
- Set "ALT" on images
- Make sure page title, keywords and description match page content
- Avoid broken links
- Void ? in the URLs. Many search engines ignore them
- Make sure your site has a robots.txt file
- Make sure your website comes up quickly (slow servers are penalized)
- Give useful content
- Avoid "link schemes"
- Avoid hidden text (colored same as background to hide content)