There are three simple things golfers of all standards can do to improve their golf.
1. Make your bad shot better,
If your bad shot is a 30 meter slice with your driver and you can turn it into a 20 meter slice your score will definitely improve.
2. When you have a wedge of any description in your hands, get it on the green.
How many times have you found your self hitting a wedge into the green. You have the hole at your mercy and instead of getting the ball on to the green you leave it short in the bunker or blade it over the green. This is quite often compounded by a followup bad shot as you are steaming from missing the green the first time. You may even three putt for good good measure.
3. Stop 3 putting
Nothing ruins your golf score faster than 3 putting.
If you imagine a hula hoop around the hole on long putts. Try to get your ball to finish inside the hula hoop rather than trying to get the ball into the hole.
Alternatively place a club 1 club length behind the hole and try to get four balls between the hole and the club from different distances. Say 4 meters 8 meters and 12 meters. If you get your first putt close to the hole you will 3 putt less.