Random note, the biggest single thing you can do to improve your aim is to crank down your sensitivity and learn to strafe with the target rather than try to track with the mouse. The second biggest thing you can do is stop trying to exactly track them, and instead try to predict their strafe patterns based on their surroundings so you can place shots where they're likely to be, at least for any weapon with a travel time.

These are great suggestions. It’s what I see pros doing, just really hard to get there.