Add pointer to exporter guidelines

content/docs/instrumenting/exporters.md

@@ -65,6 +65,13 @@ hosted outside of the Prometheus GitHub organization.
    * [SMTP/Maildir MDA blackbox prober](https://github.com/cherti/mailexporter)
    * [SQL query result set metrics exporter](https://github.com/chop-dbhi/prometheus-sql)
 
+When implementing a new Prometheus exporter, please follow the
+[Prometheus Exporter Guidelines](https://docs.google.com/document/d/1JapuiRbp-XoyECgl2lPdxITrhm5IyCUq9iA_h6jp3OY/edit).
+Please also consider consulting the [development mailing
+list](https://groups.google.com/forum/#!forum/prometheus-developers).  We are
+happy to give advice on how to make your exporter as useful and consistent as
+possible.
+
 ## Directly instrumentated software
 
 Some third-party software already exposes Prometheus metrics natively, so no