There is not one possible right answer to this question...it's like asking how do I become a scratch player...

Pick up a golf book and do everything exactly as written...then you have it...

To pick out one thing while leaving out the rest is useless...the only answer that holds water is that you need to practice, and practice, and practice some more...then you need to hit chips and pitches until you wear out two sets of similar wedges, and then you need to practice some more...and just practicing isn't enough...you will need the guidance of a professional from time to time, and you will experience setbacks...golf isn't a progressive learning curve...just look at David Duval...it is a funny game that really is more about the journey than the destination, since it will always seem that once you have something down, something else disappears in your game...my advice to you is to develop solid fundamentals with the help of a professional...stance, posture, preshot routine, balance, takeaway, top position, tempo, grip, ball position determination and then when things go funny you will have a foundation to fall back on...the rest; uneven lies, bunkers, uphill, downhill, sidehill, rough of different heights and textures, distance control, trajectory control, knockdowns, punches, cuts, hooks, bump n runs, hop and stop pitches and flops that land like a butterfly with sore feet are just some of the areas to work on outside of the basics...it is a complex and frustrating game which is part of the attraction, but the short answer to your question is that there is no short answer...