First thing that came to mind was something my instructor said during my first lesson: Don't become a tip-of-the-day golfer. I think he meant for me to not expect miracles from swing-tips, and to not confuse myself during practice, trying something new every other day.
Keep your head down on your putts. That is to say do not move your head for 2 full seconds after your putter hits the ball.
I´d say that for a beginner, this applies to all kinds of shots. I mean, look at the ball during your backswing, downswing and after the impact, keep looking at the spot where the ball lay. Too many strokes are duffed, topped and otherwise messed up because failing to do this.
I´m not saying that you can´t look at somewhere else, but too often beginners like me move their heads during the swing. And that, my fellow beginners, leads to those horrific consequences.
And another one - when the flag is positioned on the lower part of a two-level green, never hit your approach shot on the upper level. Too many putts and double bogies.
Irons/wedges setup/takeback tip from Harvey Pinnick's Little Red Book that has helped me recently: Start with a slightly strong grip loosely applied to the club. Setup with your hands ahead of ball and your arms roughly aligned parallel with the inner aspect of your left thigh (for right handers). Initiate the backswing with a small trigger move consisting of a forward push of the wrists. Then cock the wrists as soon as possible on the takeback. Then let it rip! . This setup/takeback routine seems to have helped me with my swing rhythm and shot result consistency.
One thing most golfers do not realize is that the pros are very strong,stronger than you can imagine. Forearms,legs,ankles,wrist and especially the core. That's why they hit 7 irons 175 yds. Keeping yourself strong is the best advice one can give a golfer. you don't see barrel chested golfers on tour, they develop themselves in the correct places and last but not least they are stretched and limber
Check your grip before and after each swing. (This helps me keep my grip loose. I have a tendency to tighten up and this makes for too much tension in my forearms and upper arms.Checking it after the swing lets me know if I have tightened up duringthe execution of the swing.
Seriously, learn how to think your way around a course. Don't just hit the longest club you can and don't take unnecessary risks. Those risks can blow up in your face big time.
(e.g. - trying to hit through that cluster of trees to the green where you can two putt and make par...or punch out, hit to the green, 2 putt and make bogey...if you don't make it through the trees, you may not be able to save bogey, so don't risk it.)