the best effective way to use these chords is to make sure they flow smoothley. In every chord there's leading tones that make you feel the need to resolve to another note. Using these leading tones properley can leave you with a very catchy and sexy chord progression.

Ex: (BASIC CHORDS) C [c e g] G [g b d]

the c in th C chord leads to either d or b of the G chord

When you use 7th, 6th, sus2, sus4, etc chords. you double the amount of leading tones.

As for a sixth chord;

Take any major chord, say A maj. The A major scale consists of A B C# D E F# G# A. All you are doing is adding the sixth degree of that scale to that chord. So instead of having A C# E, you'd have A C# E F#. The chord is now a compound of A major (AC#E) and F# minor(F#AC#) giving the chord a very mellow, or jazzy sound.