Try this as an experiment: write a melody with a major pentatonic scale, and write a chord line to go with it, using only the [one] and [four] chords.
(In the key of C, the pentatonic scale includes the notes C, D, E, G, and A, and your [one] and [four] chords are C and F.)
Okay so far? You've got your melody with its pleasant two-chord accompaniment. Now, switch the chords! Wherever you wrote a [one] chord, play [four] instead, and wherever you had a [four] chord, switch it to [one]. You will probably find that the melody works just as well with the chords reversed. As a rule of thumb, you can't go wrong accompanying a pentatonic melody with these two chords.
[one] - [four] - [one] - [four] - might be the single most popular chord progression for starting out the verse in a rock song. Why is it used so often? Well, typically a rock verse starts out not trying to go anywhere musically. The music wants to sit in one spot for a bit before it starts to go adventuring.
As I mentioned last week, you can achieve this affect by just staying with the [one] chord for the first few phrases. But sometimes it's just too boring to stay with a single chord. In that case, moving over to [four] is the next most comfortable thing. Switching from [one] to [four] gives the ear a little bit of movement, but it won't rock the boat or make anyone uneasy. Because with [four], you know it's not really going anywhere. It's not like going into town and getting into who knows what kind of trouble. It's like right next door where you can keep an eye on it.
If you want to tone down the sense of movement even more, you can keep the base on the tonic note. In the key of C, play
C - F/C - C - F/C -
And for the absolute slightest sense of movement, play
C - Csus4 - C - Csus4 -