When I was fairly young songwriter, I challenged myself to use a new technique with every song I wrote. It might be a chord or chord quality I'd never used, a wierd scale, an odd meter, nonstandard structure, a strange sound, etc. I avoided diatonic harmony like the plague; I don't think there was a V-I in any of the songs I wrote for several years.
After a while I joined a pop band, and I was increasingly called upon to be more orthodox in my writing. Eventually I learned the raw power of some of the standard chord progressions out there, and of diatonic harmony in general.
I've kind of hit a middle road now, because I got away from focussing on the chords. It's to easy to get into making songs chord-chord-chord-chord without any sense of flow. I concentrate on the flow, on the feel, and on underscoring melodies. Not just the vocal melody, either -- countermelodies, harmonies, solos, etc.
Most of what I write now revolves around conventional progressions with some well-placed "twists". For example, I did a song not too long ago where the last line of the chorus did a very typical C-G/B-Am-G-F-G-C. But I switched out the G after the Am to a D7/F#. It worked out really well, kind of underscored the lyric appropriately. On another song I was ending it C-Dm-F-G-C. But instead of that last G I used Abmaj7, and instead of holding the last C for two bars I did a little riff of C-Eb6-Dm7-C (note that all 3 chords contain a C, which was the melody note). There's lot of cool little twists you can do like that to spice up bland chord progressions if your ear is getting tired of G-C-D. I used to feel bad that I didn't like simple progressions, like I was "being a musician" about it. But I've come to realize that that's just my set of tastes and it makes me the artist I am.
