I've struggled with this question for years, and haven't been able to come up with an answer I feel good about, so the "correct" answer is probably, "consider the person's tastes and cater to them."

I do believe that it's probably not a good idea to start with the "best" episodes - they tend to break the usual format, and once you've seen them, there's nowhere to go but down.

Instead, I'm on a continuous search for the most "average" episodes - solid, enjoyable, and representative of what the series and franchise are as a whole. But I still don't have a simple answer.