Search algorithms are kept secret by most search engines (especially Google). However, these search engines do give you some clues in the form of their Search engine guidelines (offered by most search engines). It is important to read these and to identify the nuggets of information that are contained in the guidelines. Also, the guidelines provide useful information about what not to do (black-hat techniques) so as to minimise the change of getting your website banned.
Here are some search engine guidelines:
- Google webmaster guidelines
- Bing webmaster advice
- Yahoo! search quality guidelines
- Open directory editorial guidelines
- Ask guidelines