Omeka’s How To, or Codex, section offers a wide array of information ranging from step-by-step tutorials for managing your archive to more general instructions on adding and modifying PHP functions in your theme.
One good example of the nuggets nestled in the codex is an instruction on how to add an advanced search to your public site. The advanced search is similar to what is available to you on the /admin/items page, and allows one to search or browse by a specific field which can be quite handy.
Follow the instructions and paste the code into your theme’s item/browse page to give your site’s users an easier way to mine the archive.