Assuming one understands chord construction. Chords appear in major keys in various spots. Any one chord can appear in one, two or three positions. (that's what makes them modal) Likewise, each appropriate harmony. Another way to look at this, is function. An improvisational approach is at:
http://members.tripod.com/~griphon2/index-11.html

For this to work, one must have a reasonable notion of harmony. How chords are constructed, intervals, natural movements, etc.