Credit to OH Law firm, whose initial post led to this digging. Very useful to know:
Overview of USCIS intake process
http://www.uscis.gov/portal/site/usc...00082ca60aRCRD
Lockbox Q&A
http://www.uscis.gov/portal/site/usc...00082ca60aRCRD
Lockbox filing tips
http://www.uscis.gov/portal/site/usc...0045f3d6a1RCRD
