Is there one stretch I can do that hits everything?
To prevent injury and promote performance, you need to do a variety of stretches. But if I had to choose one stretch, it would be a lunge with extra movements.
HOW TO DO THE LUNGE STRETCH
Place a towel under one knee, then lunge forward with the other leg, placing your foot flat on the floor in front of you. The knee of this leg should be bent at 90 degrees and lined up over your ankle. You should feel a stretch in the upper hamstring and lower glutes on this side. Pull the foot of your rear leg up towards your bum using the hand on that side. Contract your glutes to increase the stretch in your hip flexors and quads. You can also reach up with the arm of the lunged side to deepen the stretch. Hold for 10-20 secs and repeat on the other side.