This is referred to as "SEO" -- Search Engine Optimisation. Many web sites, forums, and companies exist that aim/claim to help with that.
But it basically comes down to this:
- In your site design, use text rather than images and Flash for important content
- Organise your site such that you have pages that focus on a particular topic
- Avoid HTML frames and iframes
- Use normal URLs, avoiding links that look like form queries (http://www.example.com/engine?id)
- Market your site by having other relevant sites link to yours
- Don't try to cheat the system (by stuffing your pages of keywords, or attempting to target specific content at search engines, or using link farms)