This document discusses three approaches to upgrading from SharePoint 2010 search to SharePoint 2013 search. Approach 1 involves setting up a SharePoint 2013 search service application and having the SharePoint 2010 search center consume results from it, allowing users to take advantage of new search features with minimal disruption. Approach 2 redirects the SharePoint 2010 search center to a new SharePoint 2013 search center, providing full SharePoint 2013 search capabilities but requiring users to adapt to the new interface. Approach 3 federates search between SharePoint 2010 and 2013 search service applications, allowing external content to be searched while preserving the familiar SharePoint 2010 user interface.