Etiquette

It's not expressly against the rules to throw rocks at a fellow competitor during his pre-shot routine or to scream out profanities as he embarks on his downswing. Nor is it expressly against the rules to stand directly behind a person making a putt in order to get a good read. No, you will not find these specific situations address in the Royal & Ancient Rules of Golf, however each one of these situations is forbidden in the game of golf. If someone walks across your line or stands behind you while your making a putt, it is your responsibility to inform the person that it is improper etiquette. Course etiquette is fundamental to the game of golf. This code is not simply a set of ancient customs which no longer apply. These are aspects of the game which must be adhered to in order to preserve the game.

The following information  is taken verbatim from the USGA's web page at:
http://www.usga.org/rules/etiquette.html

Section I
Etiquette

Courtesy on the Course 

Safety
Prior to playing a stroke or making a practice swing, the player should ensure that no one is standing close by or in a position to be hit by the club, the ball or any stones, pebbles, twigs or the like that may be moved by the stroke or swing. 

Consideration for Other Players
The player who has the honor should be allowed to play before his opponent or fellow-competitor tees his ball. 

No one should move, talk or stand close to or directly behind the ball or the hole when a player is addressing the ball or making a stroke. (See also: "Where to stand" Golf Magazine Oct 2000)

No player should play until the players in front are out of range. 

Pace of Play
In the interest of all, players should play without delay. 

If a player believes his ball may be lost outside a water hazard or out of bounds, to save time, he should play a provisional ball. 

Players searching for a ball should signal the players behind them to pass as soon as it becomes apparent that the ball will not easily be found. They should not search for five minutes before doing so. They should not continue play until the players following them have passed and are out of range. 

When the play of a hole has been completed, players should immediately leave the putting green. 

If a match fails to keep its place on the course and loses more than one clear hole on the players in front, it should invite the match following to pass. 


Priority on the Course

In the absence of special rules, two-ball matches should have precedence over and be entitled to pass any three- or four-ball match, which should invite them through. 

A single player has no standing and should give way to a match of any kind. 

Any match playing a whole round is entitled to pass a match playing a shorter round. 


Care of the Course

Holes in Bunkers
Before leaving a bunker, a player should carefully fill up and smooth over all holes and footprints made by him. 

Repair Divots, Ball-Marks and Damage by Spikes
A player should ensure that any divot hole made by him and any damage to the putting green made by a ball is carefully repaired. On completion of the hole by all players in the group, damage to the putting green caused by golf shoe spikes should be repaired. 

Damage to Greens — Flagsticks, Bags, etc.
Players should ensure that, when putting down bags or the flagstick, no damage is done to the putting green and that neither they nor their caddies damage the hole by standing close to it, in handling the flagstick or in removing the ball from the hole. The flagstick should be properly replaced in the hole before the players leave the putting green. Players should not damage the putting green by leaning on their putters, particularly when removing the ball from the hole. 

Golf Carts
Local notices regulating the movement of golf carts should be strictly observed. 

Damage Through Practice Swings
In taking practice swings, players should avoid causing damage to the course, particularly the tees, by removing divots.