frankieve,

Sometimes I try these. Not that it always work. It really depends on the tune, but your ear will tell. For simplicity let's say you are playing in C. You can transpose it to any key you want.

In key of C.
* If the chord is G, try substituting part of its measures (mostly the former part) by Dm.
* If you substituted former part by Dm, try Dm7 before going to G.
* If you about to change from C to F, try Em or E, at the latter part of the measure you would otherwise play C.
* If from F to C, try Dm during the latter part of otherwise F.
* Try switching between C and Am during the measures of C or Am.
* If the progression is C-G-Am try bass of B when you play the G.
* F#dim sometimes sounds good when you transit from F to G.
* When you are about to change from G to C try this. Play Gsus4 then back to G and then C. G7 and G7sus4 in place of G and Gsus4 sometimes work better.
* sus4 and add9 played for a beat or two while staying in a particular chord also sound nice sometimes. Sometimes accentuating these chords off beat sounds even better.

Hope this helps

Shiral