Joy, here's a tip I learned from stylist Kendall Farr that has stayed with me the way Angie's Perfect Pants Length rule has. Kendall says the blazer should either mostly cover the bottom (in which case you're after a fair amount of shape in the torso) or should *not* cover the bottom. She believes you should never turn to check the rear view and see a jacket hem cutting the bottom in half horizontally, producing "two half-moons" below the jacket's hem.
Of course most of my jackets did exactly that, so when I can't quite figure out why a jacket doesn't work, I fall back on Kendall's rule.
A blazer tip I have learned on my own: if you go with a cropped jacket, don't go with narrow bottoms or you end up looking like a bowling pin. A short jacket looks better, to my eye, with a fuller-legged bottom.
And of course there is Angie's invaluable observation that when a jacket is worn over a dress, it will tend to look dowdy and managerial unless the jacket is short.
