SharePoint 2010 - Search results are not appearing

In SharePoint 2010 even though the crawler has completed its job for a particular site collection/site and when you make a search - Results are not shown. One of the result could be the association of the site collection with Search Service Application. To do that -
Goto Central Admin -> Application management -> Manage web applications - Select the web application you want to ssociate -> Service Connection (from ribbon) -> select the Search Service Application to associate. Save the configuration and redo the search.