Although not rules as such, "etiquette" defines what is expected of golfers when on the golf course. It's basically just good manners on the course. By being familiar with the etiquette of golf, and observing it, players will be better liked and respected by others, making everyone's golf more enjoyable. Players who observe the etiquette will feel more welcome in competitions and when visiting other golf clubs.
Avoid Disturbances to Other Players
Noise and movement.
First and foremost, always be mindful of other players on the course. Don't talk loudly while on the course, or make loud noises. (This obviously excludes shouts of "fore!" to warn someone of imminent danger of being struck by a golf ball.) Don't move, or talk, or make any noise if another player nearby is playing.
I'm reminded of an incident I saw during an Open Championship at Royal Troon when a player's drive had finished close to the spectators. The player was preparing to play his shot but stopped and looked towards the nearby crowd. Without a word, he stepped across to a little girl who was eating from a bag of crisps. He gently took the bag from her, laid it down out of reach, and went back to play his shot. He played, the crowd applauded, and he then went back to the bag of crisps, picked it up and took it to the little girl. As she reached for it, he pulled it back, took one, and then handed it back to her. The crowd nearby all chuckled. It was a lovely moment, without a word of anger from anyone, though it did leave two parents standing there blushing deeply!
The point is, it's very easy to forget how sound carries on a golf course, so just try to bear that in mind.
Where not to stand!
It is best to stand a little distance away from someone about to play their shot, ideally at about right angles to their intended line of play but not forward of the ball. Standing close to or immediately behind a player, where you're out of their sight, should be avoided. (If a player is unsure of where you are, it can affect their concentration.) It's acceptable to stand behind the ball looking along the intended trajectory, and someone might even request that you do this to help with seeing where a ball goes when hitting almost directly into the sun.
Talking of the sun, when it's shining, be careful about where your shadow falls. On greens it is easy to forget that your shadow could distract the player putting, so be very much aware of where your shadow is.
In short, try to keep both yourself and your shadow where they will not distract another player.
On the Green
On greens it is particularly important to be aware of where you should and should not stand. The rule is that a player must not make a stroke with his/her caddie, partner, or partner's caddie positioned on or close to an extension of the line of play or the line of the putt behind the ball. A significant advantage could be gained through watching a putt in this way. An exception to this would be a caddie attending the pin You might notice professionals' caddies helping with putting lines by crouching down behind the line of the putt, but you will ALWAYS see them move out of that position before their player strikes the ball. Although not actually against the rules, it is poor etiquette to stand along the line of an opponent's putt, extending in either direction, either behind the ball or beyond the hole.
It should go without saying that moving around when another player is putting is frowned upon. That said, I do remember a player during a practice round throwing a ball across my line as I was about to putt, trying to put me off! Happily I holed it and just gave him a smug smile.
Usually the player farthest from the hole putts first. Other players should mark the positions of their balls with a ball-marker or small coin placed immediately BEHIND the ball before lifting the ball. This stops other balls being a distraction to the player putting. More importantly, it removes any chance of the player who is putting being penalised for his ball striking another player's ball on the green.
If it's breezy and you're attending the pin, try holding the flag against the pin so it doesn't flutter. When removing the pin, place it away from everyone's putting line, and certainly not where a poor putt might run into it. Off the green or near the edge is usually a good place to put it if you are in any doubt. Remove the pin once the putt has been struck, BEFORE the ball reaches the hole. If the ball strikes the pin, it's a 2 stroke penalty in strokeplay and loss of hole in matchplay.
Hint: when attending a pin, the first thing you should do is to test that it will lift out easily! That's far better than panicking if it gets stuck when you try to pull it out and the ball is homing in on you!
Do not step on the line of another player's putt! That's a sure way for an inexperienced golfer to annoy an experienced one. Try to remember where each ball-marker is and avoid stepping on or near the putting line from that spot to the hole.
Marking the Ball
Although there is no actual rule stating that a ball-marker must be placed behind the ball (the side farther from the hole), this is the way virtually everyone does it. If you see someone marking the ball with the marker on the hole side of the ball, make sure the ball is replaced appropriately.
Moving the Ball-Marker
If your ball marker is on or near the line of player's putt, you may be asked to move your ball-marker. The accepted method is to use your putter head. Place the heel of the putter head by the ball-marker, lined up with something that won't move. Take the ball-marker away and place it at the toe of the putter. Occasionally you may have to repeat this to clear the ball-marker from the putting line. Remember to go through the process in reverse before replacing your ball.
During the 1977 Open Championship at Turnberry, I heard one of the scoreboard attendants shout to Tom Weiskopf as he was about to putt. He had earlier moved his marker out of the way of another player's putting line, and the lad who shouted hadn't seen him put the marker back, so was concerned that he was about to incur a penalty. In fact, he HAD replaced the marker and the scoreboard attendant hadn't seen him do it. Tom Weiskopf was known to have quite a fiery personality but, thankfully, he seemed to understand that he'd been interrupted with the best of intentions!
On the Fairway
When you are allowed to lift a ball on the fairway (for example, when preferred lies are in force), pushing a tee peg into the ground in front of the ball (the side nearer the hole) is perfectly acceptable. The idea is that when replacing the ball in line with the rules, the marker (tee peg in this case) doesn't get in the way, making it easier to place the ball within 6 inches, not nearer the hole.
Preparing for the Shot
All the comments above about noise and movement should be applied not just to anyone in the process of playing a shot but also during their preparation for the shot. I have known people to talk right up to the moment players begins their swing, or to swish away making violent practice swings while another player is going through their preparation for a shot. That shows no understanding of the game, no respect for someone else's concentration, and is very poor etiquette. It will certainly win you no friends.
I even knew one player, notorious for his chatter throughout a round, who once talked right through his own swing, barely pausing as he struck the ball, so keen was he to get the point of his story across. (I should mention that he did have the courtesy not to do that during anyone else's shots so we all had a good laugh about it afterwards!)
Avoid Holding up Play...
A lot of golfers are guilty of not calling through quicker players behind them, or when searching for a lost ball. If a gap develops between you and the group in front, and those behind you are being held up, you should most certainly call them through. Try to do so where it is safe and where you can continue your own play with undue delay. You might consider playing your tee shots and then suggesting to the group behind that they play through when ready. Stand well clear when they are ready to play, and watch carefully where they hit their golf balls.
If looking for a ball and the group behind are waiting to play, call them through immediately by clearly waving them on. Make sure at least one of your group watches closely for any ball coming close to one of your group.
Clear the Greens Quickly
Avoid delay when finishing a hole by clearing the green and moving to the next tee before marking your scorecard. Standing on a green while filling in your score is a sure way to get yourself a bad reputation! You can also help to speed up play by thinking about where you leave your clubs while putting. If possible, leave them somewhere near your route to the next tee.