You might have noticed that the line "for what it's worth" doesn't ever appear in the song itself. Nonetheless, the title does seem to make sense; the speaker in the song is asking listeners to look more carefully at their surroundings but is not telling them to follow a specific path or do anything a certain way. "For What It's Worth" captures that tone of thoughtful, friendly, non-intrusive advice.
This title, it seems, was little more than a stroke of luck. Charles Greene, the producer for the track, recounts that Stills said something along the lines of, "Let me play you this song for what it's worth." When he learned that Stills hadn't thought up a name for it yet, Greene insisted that he had, in fact, already named it.* It was another record exec, Ahmet Ertegun, who added that it would be a good idea if the cover for the single included the words "Stop, Hey What's That Sound," so as not to confuse record buyers (John Einarson and Richie Furay, For What It's Worth: The Story of Buffalo Springfield, 127). (*Alternate sources claim that Stills was talking to Ertegun at the time.)