Hey Friend,
I have put together a set of tabs with examples of some substitutions you could use in place of a C major chord.
In each case, you're either adding something to the chord, or you're changing the three note of the chord.
It might seem obvious with the add9 and add11 chords that you're "adding" a note to the base chord. If not, it should - that's exactly what you're doing. You are taking the C major chord and adding he nine note from the scale, which is the D note. The add11 adds the F note.
I know which notes the nine and eleven are by simply extending the C major scale a second octave (or range of notes).
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 C D E F G A B C D E F G A B C
The 7 chords add to the C major chord either the seven note (major 7 chord) or the minor seven note (for the dominant 7 chord).
For suspended chords, you change the three note - it is no longer part of the chord. You use either the two or four note to get the target chord.
I've written out the tabs changing from a C major chord to the substitution for this exercise. Some will be extremely easy to change between the two chords. Others will give you some challenge due to positioning on the neck. Get the easy ones down first, and listen to the differences between each chord pair so their unique sounds start setting in your brains.
I didn't have a chance yet to make the MP3 of the exercise, but I should have that for you tomorrow. You can use today to get your fingers familiar with the shapes.
Peace~
Dave | 
