I've been composing musical scores for a little over 4 months now, and I've found that a good rule of thumb to making an interesting sounding score is to incorporate the tonic and the dominant notes of the current key as skillfully as possible. For instance, if I'm writing in A, the tonic and dominant are A and E respectively. If I'm writing in E, the tonic and dominant are E and B respectively. I've had numerous conversations with a fellow composer, a guitar player, and, from what I've gathered, the tonic and the dominant are the two most powerful notes you can use in any given diatonic scale. Then, once you've established for the ear what these notes are, you can play around with them via half-step pitch changes in sequence, which opens up numerous possibilities for the music.
Now, this has been an observation of mine as well as a tried composing technique. I don't know if it concurs with established music theory or not because I've never formally studied music theory. I just think that I may be onto something.