Tack sharp eyes
One of the key things that I try to do when I take portraits is to focus on the eye of the subject. This is a well documented technique and works very well. Also, each lens has a sweet spot aperture for which the picture is really crisp. I find that it is at f/2.8 for my Canon 50 mm f/1.4 and f/4 for my Canon 70-200 mm f/2.8L. When I play with these sweet spots, I seem to get impressive tack sharp eyes. This is a crop from one of the self portraits that I shot with my Canon 50 mm at f/2.8. Next time, don't shoot full wide for crisp results. Go ahead and try stopping down your aperture and find your sweet spot.