Updating Your MSA So You Can Enforce It

Somewhere along the line, someone told you (maybe a lawyer?) that you can update your Master Services Agreement just by posting the changes and simply telling your customers, "We can update any of our terms and if you keep using our services, you accept those terms." If that sounds familiar to you, then you've received bad advice. Want to know the right way--the ENFORCEABLE way--to update your MSA?  Listen up.