Y'know, I've never really seen a good reason for starting people-in-general at an episode other than the first. Maybe if it's a specific person that you think would like a specific episode more, but apart from that...

Also, I would not under any circumstances start someone with Lesson Zero. Any more than I'd start them with Look Before You Sleep or The Mysterious Mare-Do-Well. I daresay the first of those mentioned is a good episode by some lights, but it is not in any way representative of either the show or most of the characters. Nor, more to the point, is it an episode I can watch comfortably.