I didn't like all the episodes in the first season, so I'll just list why I did/didn't like them.
1.01 Welcome to the Hellmouth
It had it's ups and downs, parts of it were good, while some parts were somewhat boring. It had a great introduction to the characters, especially the Slayer and the mysterious Angel.
1.02 The Harvest
I didn't really like this one, I think it was sort of just dragged out as a continuation from Welcome to the Hellmouth, maybe it should've been included in Welcome to the Hellmouth, I don't know?
1.03 Witch
The first full episode I watched, the episode that got me hooked onto Buffy. I really liked it, I liked seeing the whole witch thing, the high school/cheerleader aspect, etc.
1.04 Teacher's Pet
I didn't really like this one, because I didn't like the plot. I didn't find it interesting.
1.05 Never Kill a Boy on the First Date
I liked this one, it was interesting seeing Buffy trying to save the world, while be on her date with Owen, and the advancement of the Master and the Annointed one was interesting as well.
1.06 The Pack
I loved this one! Hyena Xander was hilarious, and that was just about the only time we got to see him like that.
1.07 Angel
I loved this episode! One of my all time favorite episodes, ever! It had so much Bangel-ness going on, it was great! And finding out Angel was a vampire was even better, and finally, Darla was staked! She was utterly annoying in season one.
1.08 I Robot, You Jane
Couldn't stand this episode. The plot just was too messy for me.
1.09 The Puppet Show
It was a good funny episode, little Sid was just too evil, LOL.
1.10 Nightmares
I loved this episode, seeing everyone's nightmares coming true was interesting.
1.11 Out of Mind, Out of Sight
Loved this one too. I felt so bad for Marcie though.
1.12 Prophecy Girl
I loved this so much! This and Angel were probably my top favorites from season 1, this episode was just too great. So much drama, and the fight with the Master was great.