The point guard position is the most important position in basketball. While basketball players are often identified by height and athleticism, a point guard's creativity, poise, and grasp of the mental aspect of the game can forge the identity of a team, regardless of height, athleticism, or even quickness of the point guard.
Given that a player has the requisite point guard skills appropriate to the level of competition in a particular league, there are 4 important aspects or phases of the game in which a point guard has very specific roles. They are running the offense, defensive transition, defense in the half court, and the fast break. Even if a person isn't innately gifted with speed and athleticism, knowing these roles will help achieve victory efficiently. Running a team efficiently is the very basis for the point guard's role on both sides of the court.
Running the offense: The quality most associated with the point guard position is the player's ability to organize the offense to the coach's satisfaction. They are the coach on the floor, as is often said. Even without a coach's direction, a good point guard should be asking themselves 'How do we score with the players on the floor?' Hence, the '1' position will usually be someone who can handle play calling, or is able to initiate a free-form offense such as 'Motion', 'Flex', 'Princeton', 'Triangle', etc., given a particular situation.. On the court, the point guard will often initiate or run the offense at the top of the key, above the 3 point line. From this spot on the floor, they must be adept at identifying teammate's abilities, be cognizant of the defense's weaknesses, and have situational awareness when it comes to the game clock, the score, and the state of their own abilities to be a triple threat with the ball (i.e. shoot, dribble penetrate, or pass).
However, what is an often overlooked aspect of point guard duties is the transitioning from offense to defense. If the ball changes possession and suddenly a point guard is on his heels transitioning to defense, what do they do?
Transition defense: A great point guard will be keenly aware that they are often the last line of defense when the ball changes possession. Limiting the ability of the other team to get easy baskets off of fast breaks is just as important as well-known defensive metrics like steals or blocks, but it doesn't garner as much attention. Hence, the best approach to handling the transition is to not take chances and force the other team to make the right decisions to score. A good rule of thumb on defense is to sprint to the opponent's free throw line to deter long lead passes and keep the opposing players in front of you, staying between them and the basket. A more advanced point guard will be able to keep the advancing opposition guessing by with their foot work, their body position, and fakes.
Remember, the aim of all this is to force the other team to make a bad decision or to slow the opposing team enough to allow your players to help you. It's not to steal the ball or take chances that allow the other team to get an easy layup. If the opposing team has to shoot a jumpshot as opposed to an easy layup, the defender has done their job at defending their basket.
If you were able to transition correctly, you now have teammates to help you to defend your basket.
Defense in the half court: If a full court press isn't called, a point guard will likely be the first line of defense after made baskets or successful transition defense. Since a point guard's typical location on defense is at the top of the key or out beyond the 3 point line defending another point guard, much of what they do is extremely dependent upon communication with the rest of the team. This is for 2 reasons: a point guard's perimeter location means that most of the action happens behind him/her, and often they are defending the primary ball handler for the other team.
Characteristics of good defense at other positions also apply to the point guard position. Heavy doses of good footwork and effort will do wonders against most players. Especially since point guards defend other point guards, they should have active hands, active feet, and as always, situational awareness of coming screens, cuts, etc.
As the first line of defense, it's imperative that a point guard work with teammates on defense well before a game. Just as a point guard assists his team on offense, the team will assist him/her on defense. Communication on where and when screens are coming is key, since most of the time a point guard will have their back turned to the action and are 'out an island', so to speak. Lastly, pre-game coordination with a teammate will help defend against those quick, creative point guards.
Fast breaks: This is one of the more glamorous aspects of being a point guard, as often the pass can lead to the score or a point guard may even score themselves. However tempting a flashy pass or a contested lay-up can be, a good point guard will always play within their own abilities. Valuing the basketball is a key underlying concept for point guards when fastbreak opportunities arise. As with transition defense, point guard should always shoot for dribbling to the free throw line. This does 3 things: it allows spacing for teammates to run along side, it forces the defense to commit, and it gives you a fairly easy shot or path to the basket if all else fails. If a fastbreak doesn't work out because enough defenders got back or there weren't any viable shots to take, the option to pull back and run the offense will always be there.
These are the basic roles a point guard should play, though this will obviously vary given a point guard's own abilities, his/her team, and by situation. Overall, it takes a fair amount of ball-handling confidence, creativity, and skill to become a good point guard. It takes a inordinate amount of practice and time on the court to truly be decisive at the position. However, if a player already has a fair amount of skill for the league they are playing, it doesn't take a great leap to become an efficient point guard. It's important to approach the game with the entire floor and the entire game in mind. A great point guard will always be the most aware person on the court.