Whichever method of communication a guy uses most should tell you everything you need to know.
if you call her at work, you're dating.
if you IM her at work, you want to be dating
if you call her cell phone, she's dating other guys.
if you call her home number, she wants you to come over.
if you send a fax, she's your boss.
if you send her an email, you want something long term.
if you send her a friendster email, you're just testing the waters.
and if you communicate with her at all using any of the above methods, you want to sleep with her.