Here is a quick and simple way to find duplicates for SharePoint documents.
Here is the solution to resolve HRESULT: 0x80040E60 error in SharePoint Search
Here is the step-by-step procedure to enable search on Last Modified By field in SharePoint Search
Here is a brief and simple description of how Sharepoint ranks a document in Search Results
Here is the correct way to add mapping for Lookup field in SharePoint.
Here is the quick way to find if your target file is indexed or not
To get the raw XML click XSL Editor button of Search Core Results web part and replace the already provided XSL with the following