Early Spider-Man comics had trouble defining what exactly his "spider-sense" is and how it works. In one early comic, he was able to use it to "tune in" on the Chameleon's location (clear across New York City in a helicopter), and in another, Doctor Doom was able to use it like a radio signal, transmitting a message directly to Spider-Man using some kind of transmitter hooked up to a spider. (To this day, it's still a bit vaguely defined. The Spider-Girl comics showed his daughter, having developed her powers earlier, being able to use her spider-sense in a few ways her father can't, such as being able to pinpoint the exact source of the danger in a way that sometimes allows her to find a vulnerability in an enemy.)
The famous quote "With Great Power Comes Great Responsibility" is the end-caption of Amazing Fantasy #15 and is voiced by the narrator of the comic rather than Uncle Ben himself. The attribution of the quote to Uncle Ben came decades later thanks to Pop-Cultural Osmosis, and in the early issues of the Stan Lee/Steve Ditko era, Spider-Man didn't dwell too much on the guilt to moroseness as later versions imply. From the way the quote is emphasized (with some likening it to Batman's "My parents are dead!"), it's often surprising how underplayed it is in the early stories. For instance, Issue 1 of The Amazing Spider-Man has Peter trying to work as a kind of performing artist in New York and parlay his superheroics into some form of income, which belies the impression from later adaptation that Uncle Ben's aesop transformed him overnight into a monkish commitment to superheroism. In fact, for most of the run, Peter was constantly trying back and forth to sort out his life, with the basic impression being that Peter was always muddled and divided about how his life would be like.
Peter's characterization was also somewhat aloof and cold, despite him still being a complete Motor Mouth when in costume. In fact, many characters noted that Peter, because of his adventures as Spider-Man, came off as having No Social Skills (especially apparent in the "If This Be My Destiny" storyline) and a Friendless Background. Later retellings of Spider-Man's early days, such as the Spider-Man Trilogy, Spider-Man: Homecoming or even the Ultimate Spider-Man comics, usually depict Peter as much nicer and more sociable, and give him at least one or two friends in high school.
Likewise, as originally written, Harry Osborn was a Jerkass snob rather than Peter's best friend. Gwen Stacy was originally a Tsundere type character for Peter Parker, berating and mocking him for his "lack of manliness" but still feeling some innate attraction to him and their few interactions were tense and stand-offish. Peter, recovering from the end of his early infatuation with Betty Brant, didn't give her the time of day. Her character mellowed out later on, becoming far more emotional and with less of a hard-edged personality.note The introduction of MJ also saw several aspects of her character change — like her hairstyle and her dance moves — to better match the more popular MJ. And for those who are only familiar with her most recent incarnations where Gwen is a scientific equal to Spider-Man, in her initial comic appearances — even up to her death — she was never depicted as having an interest in science and was only Peter's classmate in one class. This happened almost immediately when John Romita Sr. took over from Ditko. Romita having a Romance Comics background softened Peter's social life and more properly introduced the familiar Spider-Man gang.
Mary Jane was for the entirety of the Ditko run The Faceless, only being seen from the back, with Scenery Censorship, or even being blocked out by Speech Bubbles. This was allegedly because Ditko just wasn't that good at drawing beautiful women, which would explain why Gwen Stacy was so severe looking.
The Green Goblin in the original stories was a mysterious, dangerous, and entertaining villain whose schemes involved taking over the underworld of New York for some reason or another. His first appearance was a wacky adventure where he posed as Spider-Man's friend and convinced him to appear in a movie production which turned out to be a trap to kill him. He appeared in fewer issues than other villains but was easily Spider-Man's most popular villain. Much controversy has spread over the years if Ditko intended Norman Osborn to be the Green Goblin, since Ditko left on the issue directly before The Reveal, though Ditko insisted that wasn't the reason for his departurenote Ditko later attempted to put an end to the issue by pointing out various points in his run where he inserted Norman Osborn in the background so as to foreshadowThe Reveal. But more or less, the original version of Goblin was a Joker-esque madman who launched zany schemes without any of the deeper and byzantine motives and schemes that later writers would provide him. Before his trademark glider, the Green Goblin also used a small rocket he called a "Broomstick" as his mode of transportation.
The Venom symbiote changed over time as well. Originally, it was just an alien costume with stronger webbing, changing into a symbiote when the costume proved unpopular. The symbiote driving people insane wearing it wasn't even a thing in the comics - that came from Spider-Man: The Animated Series. Venom's design also changed over time, as its first appearance had the only major design change being a mouth and a row of teeth. A few appearances later, the teeth got sharper, and a long, dragon-like tongue was added in.
For that matter, Eddie Brock as the first Venom was originally much more deranged, spiteful, and outright villainous than he would be in later appearances and adaptations. Aside from one or two token lines of expressed regret he generally didn't bat an eye at the loss of innocent life (the first time he fought Spidey he shamelessly killed a cop, and in his first breakout he killed a security guard) and his ability to take criticism and hold himself accountable were downright nonexistent, a far cry from the snarky, self-deprecating Pragmatic Hero he is nowadays. As a result of his enduring popularity, however, Eddie would quickly be written as a Noble Demon and later on Anti-Hero, with Carnage taking his place as the Marvel Universe's outright insane Symbiote Supervillain. Several explanations have been offered for why Eddie-as-Venom was so different back then, the most common being that since both Eddie and the Symbiote were at the absolute low point in their lives at the time of bonding, they drew out each other's most negative personality traits. To give an idea of how much Eddie changed over time, compare Sony's official Venom movie (which draws from his 90s characterization where he first made his transition to anti-hero) with the fan film Truth in Journalism (which mostly harkens back to his early characterization) and you'll quickly notice how massively different they are.
The first couple of issues of Spidey's first ongoing operated on a Two Shorts format, as opposed to the full-length 20/22-pagers that became standard for Marvel (and DC later on). That's because they were drawn for Amazing Fantasy #16-19, but the book was cancelled with Spidey's debut in #15, and Amazing Spider-Man launched a few months later, starting with the pre-existing material.
In the first few years, throughout Ditko's run, Spider-Man's costume was red and black; black was often shown with blue highlights back in the four-color days. As the series progressed, the "highlights" slowly became the base color; John Romita's advent on the book entrenched that as canon.
Adaptions
The first live-action appearance of Spider-Man in movies or TV was the "Spidey Super Stories" segment on The Electric Company (1971). The villains Spidey encounters are... very different. In addition, the webhead was The Voiceless as word bubbles appeared for children watching the series to read.
