Once again, y'all are mixing up different subjects.
1) How to set the average tuning of the saxophone/mouthpiece/reed/embouchure/human body you've got, so that it matches acceptably with the average tuning of the group you're playing with today in the environment (temp, humidity) you're in. You select a note that's average for your horn (I recommend lower G) and slide the mouthpiece back and forth till it matches whatever tuning standard you like, then play.
2) How to make each note of the horn's range play acceptably in tune, given that many notes contain some inherent compromises. You map out where the notes are (this bit is actually optional) and then you practice, a lot, with INTENTION and ATTENTION (I recommend lots of long tones outdoors, pppp to ffff and back again over the full range of the horn) until the micro-corrections that are normal to all wind instruments become second nature. (I will point out that using a full proper airstream makes every horn play better in tune.)
3) How to develop your own approach to the horn and build up the relevant muscles and mental capabilities, so that your playing pitch is stable from day to day. You do the same things as #2. It's part of the same process. Until you have a stable embouchure, voicing, and airstream, you're chasing something that's everchanging. This is why little bitty children use big fat pencils and notebook paper with wide lines - they haven't yet developed the fine motor control in their hands to manage a golf pencil and write in script on narrow-lined paper.
4) How to assess and possibly correct mechanical mis-adjustments - you can't do this till you have a personal stable pitch characteristic; THEN you can go after wonky notes and see if there are any mechanical adjustments to be had.
A couple notes on this - because I see over and over people posting about a horn they just got and have never played and a couple notes seem "out of tune" - most of the complaints about "plays out of tune, must take to shop" would go away with the application of a large dose of that sovereign remedy for things musical - PRACTICE. LIke I said, until you know how to play the instrument, and you've got considerable experience on your particular instrument, "out of tune" is likely NOT to be the fault of the horn.
A very common fault is people playing older instruments with modern tiny-chamber mouthpieces. This makes the horn play overall flat, so they pull the MP out till it's practically falling off the horn. Then the bell notes seem sharp (because pulling out affects those notes less, proportionally), the palm notes flat. If they open up the palm keys to get those closer in tune, now those notes get "wild" in pitch and are easy to play out of tune. Screwing up the scale this way also can create interesting pitch anomalies. My Conn baritone had a wicked sharp middle E and F that went away when I used a more moderate mouthpiece with an inch shorter sounding length. Don't misunderstand me; it's not necessary to go on a years-long hunt for the unobtanium mouthpiece to get these old horns in tune. You just need to consider that a Berg 0 chamber is less likely to satisfy you than, say, a Link or Meyer.
Another issue is that older instruments may not feel quite as "slotted" in intonation as modern ones. I don't know what acoustic design changes are responsible for this. But if you don't have a stable embochure, voicing, and pitch sense, those instruments are likely to be all over the place and then you'll claim things like "those old horns are all out of tune". A story along these lines - a friend of mine sold me an old Martin alto. Now this guy is a very fine alto player, but for 10+ years he'd been playing 100% of the time on a modern horn. He tells me "this Martin has a really nice sound, but the tuning's pretty wild up top, keep an eye on it." Well, I picked the thing up and played it - perfect intonation, top to bottom, not a thing to worry about. Why? Not because I'm a better player overall, I"m not; but because I have spent all my alto playing time since 1978 on an old Conn, so I am accustomed to needing to steer the horn more constantly in between the lane lines.
Quite frankly, I think that the number of saxophones made since 1910 from companies of any reputation whatsoever, that are inherently "out of tune" is vanishingly small. It's always easy to blame the tools, but the real solution resides in the woodshed.