Major - can use major scales, pentatonic, licks, etc. that are of a major quality
Minor - same as above except use minor scales, modes, etc.
Dominant - everything else, including Augumented, Diminshed, altered (G7b5b9, etc.) scales, licks etc.
Of course, all the above apply to the root or tonic chords.
Think of the "quality" of the chord when you improvise. Ask yourself, "Which of the three sounds is it"?
When we overanalyze things we can get confused. If you keep at it long enough, the above forumla is probably where you'll arrive. Joe Pass taught me that some years ago. Simplicity is the key.
