Get in closer, many times a longer lense 70+mm helps.
The Canon 70-200f/2.8 shot wide open excels at this especially in heavily back lite shots.
Of coarse you can always crop if it was a good shot to begin with, but the AF lock/subject focus may not as precise as when more of the frame is filled by the subject.
Generally try to get the AF lock up on the eyes.
Model and people shooting is the hardest type of shooting there is as far as I'm concerned.
#6 and #8 are my favs