I'm a life-long coffee lover, but.... some sort of switch flipped in my head when I was about 28 or so, and I had my first great cup of coffee. From what I know about it, it was dumb luck and the stars aligned and the angels sang, and rainbows glinted off every shiny surface. Because it shouldn't have been a good cup of coffee.

Seriously. It should have been a barely drinkable cup - It was pre-ground coffee provided in a metal foil bag from a giant food service (probably Sysco but I don't remember for sure as this was 24 years ago), and brewed in one of those huge cylindrical canisters with a spigot at the bottom (probably percolated?). It was rich, sweet, unflavored coffee with an unbelievably chocolaty flavor. I had 2 cups and braved the jitters and had a third. I even chased down where they got it before rejecting it due to food service quantities being out of the question for one person.

Back in those days, I drank Burger King coffee which was probably the best of the fast-food coffees, decent but not great. Then they switched to Seattle's Best and it instantly turned to swill. I was about 40 when that happened. So I started brewing my own. That would have been about 2009 or thereabouts. Since then, I've brewed the very rare excellent cup, but that excellent cup remains my unicorn - it's still far too rare. Most of my cups are mediocre (wildly, wildly better than any fast food, gas station, or big-name coffee chains, but that's a pretty low bar). My mediocre cups are certainly drinkable brews, but I want better. I AM doing much better these days. I get good cups regularly now, perhaps 1-2 times per week. Very good cups 1-2 times per month, and excellent cups a few times per year. My excellent cups are about as rare as they ever were - it's just that my good and very good happen far more often than they did in the first 5-6 years.

I started out with a Chemex, then moved to a v60, then Fellow Duo and other immersion methods, then Aeropress, and now after all these years I've gone back to pour-over, and in my quest to get a good cup, I've decided the master the the Stagg dripper. I have NEVER managed to get a good cup out of pour over in a consistent manner. Always hit or miss, usually miss. So, I'm approaching this with an eye toward consistency:

1. Consistent prep: I place the filter in the dripper, the dripper on the carafe, pour boiling water (210F rather than 212F as I'm at 1200 feet elevation) to fill up the dripper, fill my coffee cup, then re-fill the dripper. Pour out the pre-heat water, and begin my brew.
2. Consistent movements: As per that one guy everyone is talking about, I pour in a spiral, from center out to edge, back to center, then back to edge. I haven't found a good way to do the swirl - So far my bloom is too thick to swirl much even at 3x the amount of water to grounds. I also make a nice deep hole in my bed of grounds before pouring (that helped a surprising amount in improving my brews).
3. Consistent pours: I do 4 pours including the bloom (so in the ballpark of 50, 115, 115, 115 grams) but not exact. I'm aiming for 400g of water.
4. Consistent draw down: I'm using a perforated metal disk at the bottom (a flair espresso dispersion screen) to prevent filter from clogging brewer, and doesn't rely on me remembering to tug the filter up.
5. Consistent brew temp: 205F/96C

I'm not worrying about bypass at this time - just using Fellow's filters and I'm leaving them fluted/pleated, and not folding them back against the brewer. I'm not convinced it'll makes much of a difference. I always diluted my Aeropress cups a' la Americano, (by varying amounts depending on the concentration of the specific recipe) and it made cups that ranged from good to very good and occasionally great.

I am doing consistent ratios as far as it goes, but the finer the grounds, the higher the ratio I prefer. In a submersion brew, I tend to prefer cooler temps (185F/85C), longer brew times, and a 1:16 ratio. But as I work my way into finer and finer grinds in pourover, I've discovered I prefer a different ratio: 1:22. I also prefer higher temps, but I'm just using 205F as my standard.

I saw a James Hoffman video where he said he likes grinding for pourovers on the ODE at a much finer grind than the diagram on the Ode lists for pourover, and someone here (I have no idea who) said finer grinds release more sweetness, so I decided to go from MUCH too coarse, and brew each day at one step finer until I hit the grinder's finest grind. I found some surprising results: As I stepped down each day to one notch, it started watery and sour, then got better, and better, then worse, worse then BETTER again (it was surprisingly better - and I paused at that level for several days - it repeated itself), then worse again. Not taking it through the bigger range in the past meant I missed some good spots. I had to adjust my ratio about half way through that because my 1:16 was producing some WAY too strong coffees.

So lesson learned. Start much coarser than you think you need, then step through it to a point much finer than you think you need. If you don't do that, and just zero in on the first good spot you find, you might well miss the second (and better) sweet spot that is yet to be found.

But that moving target of ratio to grind size, that worries me. I think to find the best combinations, you'd have to start with one variable and keep everything else consistent and then repeat that for each of the variables. Then you would need to vary things in groups, and you'd have to do that for each brewing method. At X grind size and Y temperature, what are the other best variables? That's hundreds and hundreds of brews and at one cup per day? That will take me a really long time.

I'm guessing that ratio isn't my only moving target - I suspect strongly that I'll prefer different brew temps at different grinds, and different brew temps per brew time, etc.

So, I guess I'm asking this: How do you work through the variables to get your best cup? And what items are ok to take short cuts, and what items do you NEVER neglect when perfecting a cup? I'm not looking for complicated recipes, more like a methodology summary.

I'm one who basically likes to keep everything the exact same and only vary grind size. I'll sometimes experiment with technique and Brewers, but in general I keep everything consistent and just change ground size to get to the overall extraction that tastes best to me. I tend to believe that all the technique / parameter changes are mostly just changing extraction yield, not bringing out some certain element of the coffee. For instance - using lower temp water is just extracting less, which could come in handy with an overly dark roast, but you could also just grind coarser with similar result.

I measure extraction with an atago refractometer. It definitely has helped me dial in coffee's quicker and learn my taste preferences as far as extraction goes. Based on your post it sounds like this could come in handy for you - seeing how changes in your technique/ brew parameters effect overall extraction.