Search functionality

There should be no more than one search field per page (except in special circumstances, such as local content searches such as FAQ sections), and they should appear in a consistent location or manner
Specific search forms should appear at the top of their relevant sections (under or near the relevant heading) to indicate their context specificity
A generic site-wide search can be accompanied by an ‘Advanced Search’ link (or button) either after the search form or below it, whichever is more convenient for layout.
Search forms which are system wide should appear in the banner / header of the website system, usually aligned to the right (or centered, depending on layout) of the page’s content

Good Practice Guides - Service Providers