Here in NYC the Museum of TV and Radio has some episodes available to the viewing public. I would guess that these were chosen to give anyone who has no idea what the show is about a basic primer in the series. For a long time they had these 8 episodes:

Pilot
Soap Box Derby
Samantha's Power Failure
Samantha's Good News
Serena Stops the Show
Samantha's Old Salem Trip
Samantha's Magic Sitter
Serena's Richcraft

They later added these two:

A Vision of Sugar Plums
forgot the title- its late in year 2 with Richard Dreyfuss as a warlock who turns himself into a dog

If you were archiving the 8 most definitive episodes or the 8 episodes that would give a novice a pretty good idea of this series would you choose these 8-10 or others and why? Soap Box Derby is nothing really significant nor is Samantha's Magic Sitter, there are no Aunt Clara episodes in this bunch, only 3 each with Endora or Larry Tate, none with Louise or the original Mrs Kravitz and from the first 8 only 1 black and white episode and only 2 with Dick York.

well I would say that if you wanted to get the basic flavor of the show certainly include the pilot but also some of the very early episodes such as Mother, Meet What's his name and A for Aardvark. I think Charlie Harper, Winner is a good inclusion and If They Never Met--I like the episodes which focus on the love story. Three Wishes is also a good inclusion.