Logical Reasoning: Necessary and Sufficient Conditions

LSAT Blog reader Vicky recently wrote with the following:

"I know you have already covered the sufficient and necessary conditions quite extensively, but there are still many (myself included) who are still stymied by it.

If you feel that the explanation I provide below is accurate and acceptable, posting it as an introductory Logical Reasoning topic might help other LSAT students."

I found