First of all, if you are writing modern songs, do not worry about figured bass or parallel fifths/fourths or any of that. That is for Classical music. While classical music can definitely influence great pop songs (Queen, Mika, Regina Spektor off the top of my head), there are different theory "rules" and terms that don't equate in traditional harmony. This is why at Berklee we had theory/harmony and if we wanted to learn counterpoint we took trad harmony. They were very different.
That said, you can vary whether your hand goes up or down for a chord for effect, and experimentation will give you a sense of the subtle emotional impact that can give, but what I want to suggest to you, Dan, is that you try learning to change chords in one position. Its called voice leading, and it can make your playing and writing sound very mature. If your right hand holds CEG, in any order, inversion has an effect, but for the sake of argument its irrelevant here, the G chord will have the note G in common. So keep your finger on the G when you change from the I to the V chord.
Next find the nearest note for the remaining two notes. Depending on the inversion (and it doesn't have to be a real inversion, maybe you double up a note or have a color tone in there- again irrelevant for now), you will move your "E" finger to "D" and your C finger to "B."
This is just scratching the surface, but its a method most advanced players use a great portion of the time. From there you can choose to change octaves, voicings, etc. for effect.
I could go on and on about this...