I think it pays to study the chord progressions of great songwriters. I always think one of Lennon and MacCartneys talent, came from understanding how to vary their chord progressions around the root chord. ie If the song is in G - then G is obviously the axis around which all other chords orbit. Sometimes of course they changed keys or modes during a song, but their understanding of form and keys was second to none.
Its a nice trick sometimes to borrow chords from another key - so say you are in F - and you :come up with;
F Gm7 C Bb
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Then a nice variation is to vary the F chord with either a minor version - or a dominant; like;
F7 Bb C7 F
So you are borrowing F7 from Bb major.
Or you can borrow a chord from a completely different key - say D from the key of G or Gminor
F D Gm C.
Hope that helps a bit!! Just be aware in your songs, that it never hurts to be consistent - but a little variation is good.
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