Because I love Steve Rogers very, very much, because I'm a dialogue obsessive and because I found him frustratingly hard to write, last year, after Captain America: The First Avenger came out, I made an audio dialogue file of all his most important lines.

Analyzed and linked here are Steve's most important lines of dialogue from Captain America: The First Avenger, as an aid to writers who want to write Movieverse Steve*. At less than 10% of the runtime of the movie, this counts as fair use for educational purposes.
This post was created with the transcription aid of yunafire.

Analysis:

Because Steve Rogers, even before the serum, never hesitates to tell anyone what he thinks, it's easy to miss the fact that he doesn't actually talk very much. He always makes his opinions known and he's happy to talk with friends, but he doesn't need as many words to do it. Captain America has fewer lines in his own movie than Black Widow has in The Avengers.

Because of this, and because it shows him in a wider variety of moods and contexts than The Avengers, I've decided to transcribe and analyze his dialogue in Captain America: The First Avenger instead of The Avengers.

Steve tends to speak in short, slightly choppy phrases and sentences, and is prone to dropping unnecessary words, particularly at the beginning of sentences. (Not always, but generally.) See: "You start running, they'll never let you stop. You stand up, push back. Can't say no forever, right?" and "Got hit, couldn't shake it." Much of the humor and emotional content of his speech is carried entirely by tone of voice, which, while not wildly dramatic, is extremely expressive. His joking tone is wry when he's feeling down, sly when he isn't and usually self-deprecating either way.

More analysis, a dialogue transcript and accompanying audio file here.

* All analysis is only intended to apply to Steve Rogers in the Marvel Cinematic Universe, not any other incarnation of Steve Rogers.