Step 1: Watch all 10 hours of original footage, scene by scene, grabbing along the way every clip containing anything even remotely funny. This generated for me a 3-hour long timeline.
Step 2: Chop away the not-funny bits from each individual clip (all I did in step 1 was save entire clips, each of which often had only a few seconds worth keeping out of 1-or-more-minutes of footage; that left a LOT of extraneous material to trim).
Step 3: Re-watch each scene's clips together, and remove the less-funny ones. Sometimes I questioned my judgement from step 1 - "why did I keep this clip? It's not even funny". So I deleted those from the timeline altogether.
Step 4: Trim, trim, trim. My first pass from step 2 was "dec" ("half decent") and gave me a good starting point, but now seeing all the clips together I could delete even more seconds by putting repeated outtakes of the same shot next to each other in quick succession. For example: Hermione hitting Ron in the wand shop, Hermione and Pansy shoving each other in the sorting hat scene, the students reacting to Neville later in that scene, and Hermione and Draco walking away together in one of the final scenes.
Step 5: Lather, rinse, and repeat step 4.
Step 6: Adjust audio. I didn't want to spend too much time here, knowing how few people probably would watch the video, but, I still wanted to fix some of the audio issues, like, the glaringly distracting ones. These included instances of noticeably bad costume noises, bumping up many of Draco's quieter throw-away lines, boosting overall dialogue levels, and lowering the volume on any screaming.
Step 7: Re-watch the whole thing as a "last looks", then export, upload, and post on my website (and here on my blog). The entire timeline ended up being 1 hour and 14 minutes long.
Now you might ask, "was this the most important or urgent project to which I could have devoted my time?" No, of course it wasn't. That's why I only edited in my spare time, and only when I felt motivated to work on it. Which is also why it took multiple years. All that said, I'm very happy finally to have a finished product, and finally to cross it off my todo list! And, obviously, to watch the finished product myself and laugh and laugh and laugh.
When I shared the finished outtakes with my friend Shawn (who played the broom store clerk), he wrote back, "I had forgotten how much fun and completely unusable material we got from the broom store scene." Soon after, he posted a Facebook status about something he was grateful for: "Outtakes and bloopers. Many, many moons ago, Jeremy Gustafson made a movie about Harry Putter. (Kinda like Harry Potter, but better.) Jeremy's policy: keep the camera rolling and see what happens. The result? A fifteen minute movie with over an hour of outtakes and bloopers."
That about sums it up.