I would recommend making "potential converts" listen to The Dance, and if possible, have them watch the video. Silver Springs is what hooked me. I'm 22 and I was 16, a junior in high school at the time. I don't think I was the only one either, because I have met quite a few people my age that fell in love with the Mac at the same time.
I also definitely agree that a lot of the Stevie solo stuff is an aquired taste. For example, my favorite album of hers is Rock A Little (I know, weird), but most people upon first listen would think it was an 80s disaster. So if you're trying to hook them on Stevie, I would start with the FMAC and then point them in the direction of Belladonna (it's definitely the classic Stevie record) and TISL.
This may seem silly, but I think it helps to tell a few Stevie/Lindsey/Fleetwood Mac stories...the drama and relationships of the group definitely add to the music and give it greater meaning...a combination of endless playing of Stevie songs and telling stories of the Mac and its members finally converted my freshman roommate. One day it finally clicked, she now worships Stevie!
Good luck!
Erin