Guy Gardner was introduced in Green Lantern 59, from 1968. He was created by the same creative team than created Hal Jordan, Broome and Gil Kane.
In that book, we find out that when the ring selected Hal Jordan, it had found two people equally worthy of the ring: Hal Jordan and Guy Gardner. Jordan happened to be the one closer to the site of Abin Sur crash, so that’s why he was selected.
Guy Gardner plays an important role in the post crisis Justice League by Giffen, DeMatteis & Maguire, where he plays a obnoxious character who believes himself over the rest of the Lanterns, and has many, many funny moments with this league (if you haven’t read it… you should! Click here to find these books on Amazon)
After this, Gardner confronts Hal Jordan to reclaim his title as Green Lantern of Earth, and the loser should quit the Corps. Gardner loses to Hal, and he surrenders his ring.
After that, he manages to get a yellow ring that belonged to Sinestro. Later on, he wears an exo suit and even opens his own superhero themed bar, Warrior.
During the miniseries Green Lantern: Rebirth (click here to buy it on Amazon), Guy Gardner recovers his Green Lantern power ring and returns to the Green Lantern Corps. After that, Guy’s always been portrayed in the Green Lantern Corps comics, being one of the fans favorites.