How do the Greasers learn more about the Socs?

The Greasers in the book are the poor kids from the "wrong side of the tracks" so they don't really know much about their rich enemies, the Socs.

The Greasers (specifically Ponyboy and Johnny and Two-bit) find out more about the Socs when they go to the movies and meet Cherry Valance and her friend Marcia.  They hang out with the two girls for a while and find out that they are not really all that different than the Greasers -- just that the Socs like the Beatles more than Elvis.

They do find, however, that the Socs are less emotional than the Greasers and that they (at least Cherry) feel like their lives are less meaningful.

The other way Ponyboy, at least, finds out more about the Socs is when Randy, the friend of Bob (who Johnny killed) talks to him a couple times -- once before the rumble, and once at Ponyboy's house.  When he does that, he finds out that Randy has some of the same feelings he does about fighting and that Randy feels like he's let his dad down.