My method uses the principle that to lower your golf scores, you must minimize the holes where you make big numbers (doubles, triples, etc.). To accomplish this, we have to know which holes that we make the worst scores on. And this requires that we have a way to measure which holes give us the most problems and contribute the most to our wasted strokes on the course.
To accurately and objectively determine which holes hurt your score the most, save your 5 (or more) most recent scorecards. Once you have at least 5 (8-10 would be ideal) scorecards, figure out your average amount over par for all 18 holes. For example, if your five scores on hole one are 5, 5, 4, 6, 5, and hole one is a par four, then your average over par for this hole would be 1.0 (a spreadsheet works great for this but you can also just use a paper, pen and calculator to do this if you want). Next, rank from 1-18 your average amount over par in descending order (highest average over par first, lowest average last). This will tell you objectively which holes give you the most problem on your home course.
When I used this method with my scores and with those of my regular playing partners, it was interesting to see that the toughest holes for each person were varied greatly from individual to individual and they were also very different from the toughest holes according to the handicaps of each hole according to the scorecard. Some people tend to struggle on par 3's, especially if they have trouble hitting their irons consistently, others struggle on holes with intimidating hazards or out of bounds.
After you have determined which holes you have the most trouble with, start thinking about what causes your high scores on those holes. Do you hit the ball out of bounds or into a water hazard on this hole? Do you often hit a fairway or greenside bunker on this hole? Do you leave your approach shots where you can't get the ball down in two shots? Do you often hit in the trees on this hole? Do you 3-putt (or worse) on this hole often?
Once you have determined what causes these big numbers on your worst holes, come up with a strategy that will help you avoid these big numbers in the future. You may have to use a 3 wood (or even an iron) off the tee to help you avoid missing the fairway or going out of bounds. If it is an approach shot to a green on a par 3, 4 or 5 that is causing you trouble, you may have to play away from a water hazard or bunker, even if it means playing away from the pin or even playing to miss the green in a spot that will give you an easy chip. If it is a green that you often 3-putt, you may have to focus more attention to leaving yourself an uphill putt that you are more likely to one or two-putt.
When you are starting to use this method, start by working on your worst 2-3 holes until you improve your average on these holes. By using a smarter strategy on these holes, you may even be able to turn these holes into your best scoring holes! Once you have improved your score on these holes, move on to your next "big number" holes and work on your strategy on these holes.
For some ideas on how to play smarter golf, there are many great books out there to read. Some of my favorites are "How to Play Your Best Golf All the Time" and "A Round of Golf", both by Tommy Armour, "Strategic Golf" by Tom Watson and "The Elements of Scoring" by Raymond Floyd.