Screen sharing and file sharing have minimal effect when dormant in background (ie when not in use)

Agreed - not to use them in show time - but they are essential tools during setup... I usually leave them enabled (but inactive) with no loss of performance...
However, if you only have one Mac and no network connectivity - then you might as well disable them...

Also:
- disable screen saver
- disable all notifications when inserting CD/DVD
- disable disk powerdown as part of energy saver settings
- diable time machine
- disable bluetooth (unless using BT mouse!)
- disable mouse zooming
- disable expose & spaces
- disable all keyboard shortcuts (except screenshot)
- disable any login items (unless necessary)
- disable auto software update
- disable flash

Basically - go thru system preferences and turn almost everything off...

S