I generally concur with most people's recommendation of showing the "best" or most "classic" episodes. Maybe pick 2 or 3 from each series, like "The Trouble With Tribbles," "Space Seed," and "Edith Keeler Must Die" (sorry, "City On The Edge Of Forever") from TOS, "Measure Of A Man," "Best Of Both Worlds," and "Tapestry" from TNG, etc... The classics are "classic" for a reason. Once they get a taste of the variety, then if they're hooked choose a series and run with it...

However, if your friends (and girlfriend) are awesome and trust you like they should, just start at the beginning... :)

Less than two weeks after my girlfriend moved in with me, she said, "Hey, let's watch Star Trek!" To which I replied, "All of it?"

"At the beginning," she said.

"In correct chronological order?!"

Her emphatic "YES! Is there any other way?!" convinced me she was a keeper. 1.5 years later, she's my fiancée now, and we're 4 episodes away from the end of Voyager Season 6... :D

So, if she doesn't flee in terror, put a ring on it!

This show definitely has tremendous acting. For one thing, Scott Bakula is amazing. Compare his performance on Enterprise to Quantum Leap; he has an amazing range, and Captain Archer is so different from Dr. Sam Beckett that I even forget that it's the same actor. Star Trek has always been known for having great acting, and this series is no different.

Have you even seen any of the 3rd or 4th seasons? I will admit that the first two seasons were not the greatest television ever produced, but that has been true of EVERY Star Trek series, including The Original Series. I'm completely surprised that both TOS and TNG made it past first seasons. The first two seasons of Enterprise were definitely better than the first two seasons of TNG, and I think that was one of the greatest television shows of all time. Enterprise has finally found its rhythm, just like TNG did toward the end of the 3rd season. It would be a shame to cancel it now.