When I was watching the show for the first time, I was surprised by how balanced the pacing of the show is (at least in the first season and part of the second season). Sometimes camera would linger for a lengthy period of time on an object while our protagonists stare intensively and silently (The Cobomite Maneurver for example) for minutes! Today many TV shows and movies are filled with loud explosions, non-stop actions and deafening soundtracks! Now I have nothing against big loud action films that are better than average such as Star Trek the new movie. I just hope more people can have the patience to sit through those silent scenes when nothing seems to happen, but tension gets built up little by little.
Hitchcock famously gave as an example of suspense a card game with a bomb under the table. You know the bomb is there... but not when it will go off. Watch some of his movies, and you'll often see someone on the run or hiding something, and the discomfort grows to sheer terror as he simply goes about his business, knowing that at any moment he could get caught. Have a look at the Alfred Hitchcock Presents episode One More Mile to Go, if you get a chance.
http://www.youtube.com/watch?v=W2uwXyKyegk
http://www.youtube.com/watch?v=Xt0-OFr1zQg&feature=related
After all, what is a plot without a buildup, an ultimate climax, and a denouement?
For example, Balance of Terror is one of my favorite episodes, not only because its war games remind me of one of my all time fave movie Das Boot (but hey, the movie came into existence after Star Trek)
It's widely thought to be based on The Enemy Below.