While setting up search, we create a seperate search site. On this site, on the results page, we can set up any customizations we want. We can modify the xslt, set up refinements etc. On our default master page, the search box redirects us by default to the osssearchresults.aspx page. But, we want to be redirected to our custom search page.
A simple way to achieve this is to go to your site Collection, go to site settings - Under Site Collection administration, choose 'Search Settings'. On this page change the 'Site Collection Search Results Page' to 'http://.../search/results.aspx' or whatever is your custom search page.