What is your practice technique?

Two and a half years ago I was a 34 handicap in golf(that's pretty dang bad). I could advance the ball great (knock the heck out of it) but my scoring was awful. My nephew (a playing professional)took a interest in my game. I'd spend hours at the driving range hitting A TON of balls. Some of them well, but far to many went places I hadn't intended them to. The nephew spent maybe 90 minutes with me over the next few months. During that time he drilled practice techniques into my thick head. Other than the solid fundamentals like grip, posture, stance (do you see the parallels with pistol shooting?) I learned why my shots did what they did and applied corrective measures when needed. Today I hit far fewer balls at the range. My distance and accuracy have improved greatly. I practice "play conditions", meaning each shot means something. Solid, consistant pre-shot routine. Today I'm a 17 handicap (still not good enough)who shoots in the mid 80's in tournament play. What practice techniques do you veteran competition shooters find truly effective? Thanks in advance