One way to put automation to work is by making it easy for you and your users to follow standards in AutoCAD. That is what this routine from Bob Qualls does. It allows you to attach an xref in much the same way as you probably do now, except that the xref will be created on a new, unique layer and that layer will be locked.
Start by loading the LISP file, then type in the command LNL. At this point, proceed with selecting your drawing to xref; when you are done, it will be inserted on a new layer named XR_<name of drawing>. Feel free to rename the LISP function to XR or whatever your current shortcut is, and to customize the layer name to fit your needs. Good job, Bob.