What was your first tweak?

My first tweak( of the audiophile age)was applying green marker to the edge of my CDs, follwed soon after by the rubber discs that fit on the top outer edge of a CD.
The flat discs that were held on to the top of the cd with adhesive was probably my first tweek. They did improve clarity in the treble. Next came the reference bands that stretched on to the outer edge. They were good too, easier to use, and removeable. I would still be using them, but I got a Pioneer PD-S95 transport that clamps the disc, and makes their use redundant.
Green edge on CDs.
I used a common paint pen.. Not the 'audiophile approved' pen, so obviously my painting was for nought. As only 'audiophile approved' spending counts for anything.
Making cheap tweaks out of simple junk will not do...
The tweaks have to be made and approved by 'experts, and have to cost at minimum 100 times what they cost to make.. to be an genuine 'audiophile' tweak.
Headphones. None will bother me cuz I hear nothing.
Way back in the dark ages, I read that tonearm damping was the coming thing in consumer audio. We just called it hi-fi. Must have been in the early 60s. I had an Empire turntable and arm, and the article I read said to get a paper clip, bend one end tightly around the arm -- more or less at the arm'smidpoint -- and set up a dish of some kind (I used the top of a Shure cartridge box, upside down), and fill it with STP. Then stick something on the bottom of the paper clip that acted as a little paddle when the contraption was lowered into the STP goo.

Well, darned if it didn't work, or at least I thought it did. Amused my friends, too.
Way back when (around 1990) I sent my Philips CD-80 to Stan Warren and had him mod it for me.
It worked. The sound was more open, detailed and dynamic.
Green marker followed by rings.
Placing a dime on the tone arm to stop those annoying skips!!!!!!!
My first tweak was adding sensory deprivation when I put my stereo in my closet, sat inside in the dark with the door closed and my headphones on listening to CSN's Suite: Judy Blue Eyes. I listened to every single note on those guitars, individual voices in harmony. I was fourteen years old and I thought that Garrard turntable and TEAC cassette deck were the coolest.
Cardas speaker placement then rubber/spiked feet, green marker, tube rings, power cords, Porter Ports, Tone arm rewire in that order.
I liked a little more tracking force so I used nickles and quarters. Dimes just wouldn't do the trick!
2nd: Ferrite rings on ICs & SCs. Not sure they had any effect.
Yes, nickels on the headshell seemed to be the right weight for my TT...anyone remember wedging a match book either under or above the 8 track while it was playing so it sounded right? Just loved the click to a new track right in the middle of the song while you were listening.
Speaker cable's. I know it's not considered a tweak now but in 1972 it was, friends and family scoffed and laughed at the high quality, thick cable that had no terminated ends just bare wire. There wasn't much of an improvement in sound quality but it was inexpensive and that was important at that time. Later on, a few year's after CD players came along, putting Black Diamond cones under and removing them from the player stopped everyone in their track's, audiophile or not. I still bevel cut and green pen the edges of the little silver devil's.
Generic Tip-Toes under my Adcom 565's.
Tube Coolers. They didn't actually do anything but seemed like a good idea at the time.