One of the first fundamentals to learn the golf swing is the proper grip and rightfully so; it is the sole connection to your body and the golf club, you must have a grip within the accepted parameters in order to play golf effectively.
However, even before the grip happens, there is a less talked about fundamental which deserves just as much if not more attention, especially for people who really want to get good. This crucial fundamental is the connection from your body to the earth. Yes Footwork!! First let's define footwork as it is not merely what the feet are doing, but it also encompasses the motion of the ankles, knees and pretty much the whole leg. Most amateurs have the improper footwork. Improper footwork is the one of the first things that should be looked at to diagnose any swing flaws. Not using your feet correctly can lead to swings that are off plane, early extension with the body, casting, inconsistency, lack of balance, and improper body trunk rotation to name a few. Putting it plainly, you're going to suck if your feet don't work right! It's funny how many golf lessons I see online from top instructors try to teach certain movements without addressing how your feet should work when the solution could very much be in the feet! For example, you will find many youtube videos on instructors trying to teach hip depth, shallowing out the club path and keeping the tushline without addressing footwork!! Good luck, never gonna happen!
The Feet roll and everything else glides
In the correct foot action, your feet, ankles roll. This causes your hips to actually do what I call is gliding. When your hips glide you are much more able to get into the "Slot" much more able to get into balance and get into all the positions that the top ball strikers are getting into. I wish I had some reference video links I can point you toward, but in the meantime look at this photo of Kevin Kisner. The best way I can explain it is to imagine a skier skiing down a mountain with their skis parallel carving side to side. This is how your feet and ankles should work. This motion is highly more different that arbitrarily "Shifting your weight the front foot." So, if you really haven't paid any attention to what your feet are doing in the swing, you'll see how much if affects your golf shots' accuracy and power! Do your feet work like this?
After 15 years of teaching golf, one of the biggest complaints I get from my new students is "I can hit it well on the range but not on the course" or "The swing changes I make only last for a few days." If this is you, don't worry you're not the only one.
The reason why this is happening is because of two things: #1 the changes you are making are what I call are superficial changes and #2 Even if you are making the correct changes, you do not know how to mentally implement them in stressful playing conditions." An example could be the typical golfer who changes their grip only to find that it's only helped fo a few days, or the golfer who is able to swing in balance on the range but keeps falling all over the place on the course.
You will know real change when you see the results on the course. These changes come about when you work on the motion of the body as a whole unit, not just a superficial change e.g., in you grip, your left arm position, or right foot etc. If you learn golf or any complicated movement in this way, you end up feeling like you're doing an awkward robot dance! When you want to create lasting changes, you have to start with the motion of the body as a whole. When you learn golf this way, your grip, stance, posture, head position, and overall swing will form itself. Think about it this way: If one were to sculpt a statue the sculptor starts with the general mold of what the finished product is going to look like and then carves out the details later; In designing a car, you build the whole frame and chasis around the specs of the engine not the other way around. Don't be fooled, in golf instruction you will find that there are a lot of myths that are ruining your swing, learning the corrections will be eye opening!! Don't take my word for it, watch how my student's swings all have the classic golf swing look to them, this is not coincidence, they didn't get into that form with complicated motions, in fact many of them were able to get into those positions after the very first lesson. Then from there, making minor adjustments became a lot more natural.
This brings me to address my point #2, how do you take newly built swing and take it on the course? You must take time to practice these new motions on the course, preferably with your coach from time to time to make sure you are not going back to you old habits. It is when you're able to pass the threshold of Stress Induced Muscle-Memory where you will really start to see change on the course. Basically, your body needs to be able to trust your new motions on the golf course and you must mentally feel the postive results. The more you do this, the more you will be able to change your muscle firing patterns. I can't tell you the amount of times I can get a person to swing certain way on the range, but when I take them to the course, it all goes south! Part of Danny Lee Golf Instruction addresses strategies on how to re-wire you brain to accept the changes you've made during your practice sessions.