You might have gathered that the two other very important notes of any scale are the 3rd and the 7th. That is because those are the notes that give chords their particular function, whether that is Major, minor or Dominant. To stress these tones on a ii-V-I or most other chord progressions gives even more of a feeling of making the changes, and stresses the differences in the chord, even though the scales are the same.
This is also the time you should start to really know your chords. Here is a reference for chords. It comes from Jamey Aebersolds wonderful Jazz Handbook, which you can download here.
So, here is the way it works. Play along so you can hear how it sounds.
Bottom voice - 3 becomes
7 then resolves down 1/2 step to 3
Top voice - 7 resolves down 1/2 step to 3, becomes 7
You can also reverse it, and it looks like this
You can use guidetones for any chord progression, and they will really tune your ear to the sound of the changes. We will have an exercise in that later, and will be using the guide tones extensively. They are a great tool, along with scale knowledge.
Next we will be using all of this knowledge to use several different ii-V-I progressions together, our first attempt at really making changes.