James Potter I

James Potter was born in 1960. The early demise of his parents (both died somewhere between 1976 and 1981) and his subsequent inheritance prevented him from needing to work later in life. He was therefore able to devote his time after his graduation from Hogwarts to help fight against The Dark Lord.

Childhood
James Potter was born into a wizarding family of wealth. Both his parents were elderly, even by wizarding standards, both died under normal circumstances. He was a tall, thin boy with untidy black hair and hazel eyes framed by glasses.

School
He began to attend Hogwarts in 1971 at age eleven and was sorted into Gryffindor. While there, he befriended Sirius Black, Remus Lupin and Peter Pettigrew, and together they called themselves the Marauders. James was exceptionally bright, one of the cleverest students in the school and the ringleader of his gang.

James had great talent on the Quidditch pitch as a Chaser for his house team, and he knew it. In the first film, James was said to be a Seeker, but Rowling stated that he was a Chaser in the second Scholastic interview. Yes, the editors are aware that on a summer's day when he was 15 he was fooling around with a Golden Snitch - much more effective to impress girls than a Quaffle, of course, and something that proves nothing about which position he actually played. He was something of an obnoxious youth for the majority of his time at school, he liked to show off and was exceptionally self-confident. He habitually ruffled his hair to make it even untidier, to look as though he'd just got off his broomstick.

James had a habit of hexing innocent students for no other reason than because he could, especially Severus Snape, a Slytherin in the same year as James. James and Snape had a strong rivalry throughout their time at Hogwarts. Remus and Sirius have said that the reason this rivalry began was due to Snape's jealousy over James' talent at Quidditch and his popularity. Snape followed the Marauders around, looking for reasons to get them expelled. James, in turn, used the hexes Snape himself had made up against him.

James spent the majority of his academic career chasing after Lily Evans, a redheaded girl his age, also in Gryffindor. He couldn't help but make a fool of himself when she was around, as she was perhaps the only student in the school who was totally unimpressed by him (as well as Snape, of course).

Animagi
As second years, James, Sirius and Peter figured out that Remus was a werewolf. Rather than abandoning him (James in particular insisted this monthly hazard didn't mean Remus was truly abnormal), they spent three years learning to become Animagi in order to accompany Remus in his transformations. In his fifth year, James managed to perfect the transformation and become a stag Animagus, which earned him the nickname "Prongs."

In the Marauders' sixth year, Snape saw Madam Pomfrey and Remus going to the Shrieking Shack using a secret passage under the Whomping Willow. Snape was very interested in where Remus went every month, and Sirius told him that the trick to getting past the Whomping Willow was to poke the knot at the bottom. Snape followed Sirius' directions and was nearly at the Shrieking Shack when James pulled him back. At great risk to his own life, James saved Severus from certain death at the claws of a werewolf. This act formed a life debt between the two boys, which supposedly motivated Snape to save Harry's life in Harry's first year, however much he hated doing so.

At the age of sixteen, James' parents allowed Sirius to move in with them so he could escape his own horrible family, and Sirius soon became like a member of their family. By his seventh year, James had lost the less savory aspects of his personality and was even appointed Head Boy despite the fact that he hadn't been a prefect. He also finally managed to impress Lily Evans and began dating her at this time. He stopped hexing bystanders for fun, the exception being Severus, who in turn never lost an opportunity to hex James.

After School
After graduation, James married Lily, and Sirius was best man at the wedding. The three of them, along with Remus and Peter, joined the Order of the Phoenix in the fight against Voldemort. During the course of the next three years James and Lily defied the Dark Lord three times as the conflict continued. Voldemort never tried to get James and Lily on his side, and it's speculated that the reason was that they were too loyal and close to Dumbledore.

On July 31, 1980, Lily gave birth to their son Harry James Potter, but it wasn't long before Dumbledore found out that they were in danger. Little Harry had become a target of Lord Voldemort because of a prophecy Dumbledore had heard--and Voldemort knew about it, too, because of none other than Severus Snape. In October 1981, Dumbledore told the Potters that their best chance of remaining safe against Voldemort was the Fidelius Charm. James insisted to use Sirius as their Secret-Keeper, even though Dumbledore offered to fill the position.

Into Hiding
Sirius, however, had a different plan. He convinced James and Lily to use Peter as their Secret-Keeper, with Sirius as a decoy. They agreed and the charm was cast in secret, but this attempt at a double-bluff ended in tragedy. The only people to know about the switch were James, Lily, Sirius and Peter--even Dumbledore and Lupin were kept in the dark. Less than a week later, Peter betrayed Lily and James to Voldemort.

When the Dark Lord arrived at Godric's Hollow, James told Lily to take Harry and run, and stood to face the darkest wizard in a century on his own in order to give his wife and child time to escape. As talented as he was, he was no match for the might of Voldemort and he was killed. James Potter died protecting his family and is remembered fondly throughout the majority of the wizarding world.

Behind the Scenes
There has been some confusion about whether James played Seeker or Chaser, but J K Rowling has confirmed he was a Chaser.