just practice, if you can afford to hunt you can afford ammo to practice, practice makes you a better marksman, being a better marksman instills confidence, being confidant in your ability makes any shot you take easier, take only the shots that after an evaluation you have a 90% or greater percentage of making. This is how I roll, I've taken 64 whitetails beyond 400 yards, 28 of which were beyond 600, a handful were past 1K, confidence goes along way.
I know most folks method is point and shoot, those shots are just as critical as the shots I take, they can just be made quicker, but the way to become efficient is practice.
RR