Here is what helped me:
First, be honest with yourself and your game. Know how far you hit your clubs. Not the furthest you have ever hit it, but the furthest you can depend upon it each time you take that club out. At one time, I was hitting my five iron 180-190 yards. I don't anymore. Know your limitations.
If you want your score to drop, with very little investment, learn to putt. It costs no money except for having 2 balls and a putter that feels good to you. Honestly count all of your putts when you play. How many 3 or 4 putts are there? I would guess more than 6. If you can't putt, you cannot cut your score down, unless you can hole out from chips and holes in one. I went from the 130s to the low 100s just by working on putting.
Know the course. Based upon your skills and swing tendencies, use your fall flight to your advantage. If you hit a fade, then play a fade. If you hit straight, then play that. Plan your shots by what conditions (wind, lie, lie angle), what abilities (are you in the zone or not) and how far you hit. Also, you do not have to hit the longest club in the bag to make it there under regulation. Know the yardages of the course and how far the hazards are. I use a GPS to do that.
You need to count on your irons. You hit them more than you ever hit the driver. You will hit your wedges even more than your irons. If you cannot hit shots from 100-200 yards, you're in for a long day.
Work on the short game. You need to be able to chip, pitch and hit the target from 110 yards in. You need to know how to get out of greenside bunkers and get close to the hole.
Lastly, don't focus too much on your equipment. Let your technique, not your clubs, lower your score. If you cannot hit long irons (3-5), then replace them with hybrids or long woods. However, focusing on the newest clubs year after year get you nowhere. Since the drivers have hit the 460 cc mark, aside from the sdjustability, a hit on the driver face goes just as far and straight. A slice with an R5 is the same as an R9. Fix the swing first. focus on your higher numbered woods from the tee box, instead of resorting to the driver.If you really want to improve after working on fundamentals, get fitted by a certified Master Clubfitter.
Typed on my iPhone.