Practically every episode has a love interest for Captain Kirk. Usually it's the random alien women he meets.
Then there's other characterizations that are basically caricatures, like Chekov, and Scotty.
It seems also that every episode had to have a hand to hand fist fight with Kirk and a baddie, with that famous fight music behind them trumpeting along.
And a lot of the episode were just pure 60's cornball, like finding a planet full of mobsters, or a planet exactly like Earth but with children.
That seems to be the general idea of what TOS is (and the idea the new film remake is built on), but if you actually watch all 79 episodes, it turns out this isn't the case at all. Except for the cornball. I personally can't watch one episode of the show without cringing. But that's just because the 60s science fiction really isn't my thing.