Muggles' Guide to Harry Potter/Major Events/Quidditch captain

Overview
The House Quidditch Team Captain is in charge of selecting the players for the Quidditch team, setting practices, and coaching them in the necessary maneuvers to guide them, hopefully, to win the Hogwarts Quidditch Cup.

Event Details
There is no description of how the Captain of the house Quidditch team is selected. It would appear to be a selection made by the head of the House, presumably from among the returning team members; while it would be logical to select the most senior returning team member, this is not how the selection is made, because Katie Bell is one year senior to Harry, and yet Harry is selected as team captain in his sixth year, while Katie is in her seventh year.

In Gryffindor house, the Quidditch team captain for the first three years is Oliver Wood. There is no Quidditch in the fourth year because of the Triwizard Tournament; in the fifth year it is Angelina Johnson, and in the sixth year it is Harry Potter. Marcus Flint is captain of the Slytherin Quidditch team for the first three years, despite his apparently having to repeat a year for academic reasons; Cedric Diggory is captain of the Hufflepuff team in Harry's third year; while Roger Davis is captain of the Ravenclaw team in Harry's third to fifth year. There does not seem to be any playing position that is more often chosen for the captaincy than any other; Wood is Keeper, Flint, Roger and Angelina are Chasers, and Harry and Cedric are Seekers.

As Quidditch captain, Harry has a great deal more work to do than either of his predecessors. In Harry Potter and the Order of the Phoenix, because of the ongoing battle with Professor Umbridge, Harry was banned from the Quidditch team along with Fred and George Weasley; so Angelina did have to engineer a mid-season replacement for her Seeker and both Beaters. But in Harry Potter and the Half-Blood Prince, so many players are incapacitated or are unable to play due to detention or other concerns that both Slytherin and Gryffindor seem to field a substantially different team for every match.

Notable Consequences
As Quidditch Captain, Harry is called upon to create a Quidditch team. He has a few experienced players to draw from; Katie Bell, who was on the team as Chaser when Harry first started playing as Seeker (making her only a second-year student at the time), Ron, who had played as Keeper the previous year, and Ginny Weasley, who, though nominally a Chaser, had filled in as Seeker while Harry was banned in the previous year, are kept on, along with himself as Seeker, but the previous year's Beaters are replaced, and a new Chaser is brought in. However, this is not a static team; over the course of the year, players are injured (Katie Bell is Jinxed, Ron is poisoned, Harry himself is injured mid-game, and later put on detention) and Harry must repeatedly juggle the roster to be sure of fielding a full team.

It is during this time that Harry begins to understand how Angelina Johnson, and before her Oliver Wood, had felt about their duties as Quidditch Captain. Harry finds that it is taking a significant part of his time and attention, but finds consolation in that as Captain, he can schedule practices when he wishes so as to avoid the "Slug Club" parties put on by Professor Slughorn. Late in the year, he also finds that practicing alongside Ginny can be quite exhilarating.

Analysis
In Harry Potter and the Half-Blood Prince, we are told that many of the privileges granted to Prefects are also granted to the Quidditch captain. One question that arises is exactly which of the Prefects' privileges are granted to the Quidditch captain, and why? The only one that is actually mentioned is that the Quidditch captain can use the Prefect's bathroom. It is entirely possible that this is intended as explanation of how Cedric Diggory is able to tell Harry about the Prefect's bathroom in Harry Potter and the Goblet of Fire; there is no mention that Cedric is a Prefect, only that he is Captain of Quidditch, and Cedric being a prefect is certainly something that Cedric's father Amos, with his demonstrated excessive pride in his son's achievements, would have mentioned.

Greater Picture
There does not seem to be any particular significance to Harry's being made Quidditch captain. Presumably, he was the only logical choice for the position, as he had been considered good enough in his year to be considered for the position of Prefect, but had been passed over because he "had enough responsibility to be going on with." As the Quidditch Captain receives all the privileges of the Prefects, but with less responsibility (fielding a team and coaching it to play well), it is perhaps the case that this position was given to Harry as something of a reward.

Once Harry leaves school, he does not seem to re-enter the world of Quidditch as a sport. The same cannot be said for Oliver Wood, who apparently is picked up by a professional team (Puddlemere United) on graduation, or Ginny Weasley, who, according to an interview given by the author following publication of the final book, plays professionally for a while after she and Harry are married. We can speculate that Ginny quite possibly was Quidditch captain in Harry's absence, during his seventh year, due to her demonstrated skill in both the Seeker and Chaser positions, but nothing in the story suggests this. Whether she and Oliver are selected by professional teams because of their captaincy, or because of playing skill, is unknown. We are not told of any scouting done by the professional teams at Hogwarts games, although it is logical that scouts would be present at many school games.