As the Superman character developed, so too did his self-titled comic evolve. World War II saw Superman fighting the Axis menace, while immediately thereafter the Man of Steel spent most of his time nabbing common crooks and the occasional weird menace like the Toyman. But formulaic though these stories mostly were, it was during this time period that the character's powers, abilities, and weaknesses developed and were codified. This was also the time when the Superman TV show was popular (which explains why so many then-current stories were lame).
About 1956, however, things began to change, and the Silver Age Superman came into being. Editor Mort Weisinger, back from California where he had been supervising the television show, took a greater part in the editing of the stories, throwing more imagination and experimentation into the mix. This saw the introduction of more exotic and fascinating concepts like the mermaid Lori Lemaris; the planet-stealing villain Brainiac; various colors of kryptonite; the stories revolving around the bottled city of Kandor; and more. This period also saw the transition between the more 50's-appropriate art of Wayne Boring to the more dynamic (but still down-to-earth) style of Curt Swan, whose work would be closely associated with the character for the next two decades. The Silver Age of Superman would last throughout the 1960's.
The 1970's would see some important changes, including Clark Kent going to work for a Metropolis television station, dropping the Daily Planet background that the character had enjoyed since the 1930's. Artists like Neal Adams and writers like Eliot S! Maggin tried to breathe new life into the character, such as removing his vulnerability to kryptonite as well as much of his incredible power.
The 1980's saw radical revisions of the character. DC Comics decided to remove their multiverse in a bid to simplify its comics line; this led to the rewriting of the back story of the characters DC published, Superman included. John Byrne rewrote Superman, removing many established conventions and characters from continuity, including Superboy and Supergirl. Byrne also re-established Superman's adoptive parents, The Kents, as characters. In the previous continuity the characters had been written as having died early in Superman's life (about the time of Clark Kent's graduation from high school). The 1990's saw Superman killed by the villain Doomsday (leading to a media sensation surrounding the relevant issues), although the character was soon resurrected. Superman also married Lois Lane in 1996.