This is another area that not nearly enough of us are addressing, as most who have patello-femoral pain are only worried about isolating the vastus medialis obliquus (VMO).
In research by Ireland et al. (1), they found that athletes with patello-femoral pain had significantly decreased strength in both hip abduction and hip external rotation. How much is significant? These subjects were 26% weaker in hip abduction and 36% weaker in hip external rotation!
Now that we know what movements to train, what muscles are most affected? Specifically, we're talking about getting your gluteus maximus and posterior fibers of the gluteus medius firing. So before we do low-body work, we should be getting some activation work in to make sure those muscles are stimulated and ready to go. X-Band walks are perfect here.
You'll see in the video that the set-up is a little funky, so hopefully seeing it will make it easier than me trying to explain it! Big things to focus on here include turning the toes out slightly and bracing the core throughout. This will prevent you from using the "Weeble-Wooble" substitution pattern that typically occurs in hip abduction movements. Stay tight, tall, and use those glutes and you should be just fine.
In maintenance phases (where I'm focusing on max strength), I may only do one set before training. In phases where motor control and recruitment are the priority (for instance, in the early off-season or a transition phase), I may perform three or even four sets of these exercises before training.