Some clarification about what I'm playing in this comping study (I omitted the obvious):
Bar 3-4: I omit the bass note in these voicings (and most other voicings in this comping lesson). The 1 and the 5 are the least important notes of a chord (when you're playing with a bass instrument). 3 and 7 are the most important notes and tensions make a voicing interesting. This doesn't mean you always have to play tensions, basic chord voicings like the ones in this II V work as well. Find a good balance. Single note lines work good as well, but keep it basic (unless you are filling the gaps in a theme, then you can play a bit more active lines).
Bar 5-6: the lead sheet says Cm7 for these two bars. Something you can do to make that 1 chord a bit more interesting is using the line cliché. The line cliche is a chromatic line going from the 1 of a chord to the 6 and is used quiet often in bebop and Latin music.
Bar 6: I play the Bbm 1 beat early (on the 4). This is called anticipation and can be used to give a tune a bit more drive. You can anticipate a quarter note or a quaver (like the end of bar 13).
Bar 11: this is a basic Gm voicing. Gm is the first substitute for Ebmaj7. It would have been nicer if I had played a Gm7, so the 9 of Ebmaj7 would be in the voicing.
Bar 20: this is a very useful cliche, going from the #9 to the b9 of the dominant chord to the 5 of the target chord.
Bar 28: this basic Bbmaj7 chord voicing is the first substitute for Gm9. The next voicing, Bbmaj7#11 is a substitute for C 13.
Bar 28-31: delaying and anticipating create more interest compared to just playing on the beat.
Bar 32: I play a 6 chord here because it's the end of the chorus. A 6 chord is more stable than a maj7 chord, it's better to play a 6 when a chord requires a tonic sound.