Loading your Canon AE-1 for the first time can be intimidating. So intimidating in fact, that I once brought mine with me for a week long trip in Europe, and relegated myself to only those 36 photos, for fear I’d ruin the film while reloading.
Fear not, however, as this step-by-step guide will give you the confidence to shoot as many reels of film as your heart (or wallet) desires.
When you’ve finished your reel, pull back the lever on the film rewind knob on the top left of the camera body, and the film door will pop open. Use the mini handle to turn the reel clockwise (there is an arrow on it for the directionally challenged) until you hear that all the film has been wound back into the canister. Give it another crank or so to make sure that all the film has gone back into the canister. Leaving the tab out won’t expose any photos, however, it will make it difficult to tell whether or not it's a reel you’ve shot on already. This could lead to you loading up film you’ve already shot and double exposing the film, meaning you’ve essentially buggered not 36, but 72 photos. Not fun.
Now that your film is wound back into the canister, open the camera back by pulling up on the rewind knob. DO NOT open the camera back until you are sure that you have wound all the film back into the canister, as opening it without doing so will expose the film to light, and ruin the photos.
Now that this film is free, set it aside and grab your new canister of 35mm film. Place it upside down under the film rewind knob just like you found it, and pull the tab out and over to the other side of the camera. You’re going to want to tuck that tab into the slots on the spool on the right-hand side of the camera back. Once it’s in there securely, pull the film advance lever to turn the spool, press the shutter button, and then advance the lever one more time. At this point, your film should be loaded. You should see that the square holes on the top and bottom of the film should be nestled into their square counterparts on the spool. This keeps your film in line as your shoot through the reel.
Now that you've loaded your film, you can close the camera door, and press back down on the film rewind knob. Put the film advance lever back if you haven’t already, and you’re ready to shoot! Just remember that the first picture you take will be a dud, as the film has already been exposed to light (hence the film counter starting at an orange “0”)