Fixing up content negotiation docs

docs/api-guide/content-negotiation.md

@@ -45,6 +45,10 @@ It's unlikely that you'll want to provide a custom content negotiation scheme fo
 
 REST framework's content negotiation classes handle selection of both the appropriate parser for the request, and the appropriate renderer for the response, so you should implement both the `.select_parser(request, parsers)` and `.select_renderer(request, renderers, format_suffix)` methods.
 
+The `select_parser()` method should return one of the parser instances from the list of available parsers, or `None` if none of the parsers can handle the incoming request.
+
+The `select_renderer()` method should return a two-tuple of (renderer instance, media type), or raise a `NotAcceptable` exception.
+
 ## Example
 
 The following is a custom content negotiation class which ignores the client
@@ -61,6 +65,27 @@ request when selecting the appropriate parser or renderer.
             """
             Select the first renderer in the `.renderer_classes` list.
             """
-            return renderers[0]
+            return (renderers[0], renderers[0].media_type)
+
+## Setting the content negotiation
+
+The default content negotiation class may be set globally, using the `DEFAULT_CONTENT_NEGOTIATION_CLASS` setting.  For example, the following settings would use our example `IgnoreClientContentNegotiation` class.
+
+    REST_FRAMEWORK = {
+        'DEFAULT_CONTENT_NEGOTIATION_CLASS': 'myapp.negotiation.IgnoreClientContentNegotiation',
+    }
+
+You can also set the content negotiation used for an individual view, or viewset, using the `APIView` class based views.
+
+    class NoNegotiationView(APIView):
+        """
+        An example view that does not perform content negotiation.
+        """
+        content_negotiation_class = IgnoreClientContentNegotiation
+
+        def get(self, request, format=None):
+            return Response({
+                'accepted media type': request.accepted_renderer.media_type
+            })
 
 [accept-header]: http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html