Setting up and tweeking kick out ejector holes like in my Metallica, I had to actually slightly bend the metal curved hood to make the ball hit my flipper in the right spot. And that was after I installed the mantis protector. On my walking dead I had to raise up a ramp on one side because the ball was launching off the ramp. Sometimes it's just bending a switch to make better contact with the ball if it wasn't always registering. Those are things I consider "dialing in"

Adjusting ball guides

Basically getting all the kinks out.

By tightening everything. Making sure all the guides direct the the ball properly. All the mechanisms are adjusted.

Kinda sucks that you have to do this right out of the box. But for the best experience with your game it has to be done. Otherwise you're just hoping the factory got everything 100% right.
Which is almost never the case.

And to keep my games in tip top playing condition. I clean, wax and I check that everything is still tight above and below the playfield. Every 100 games or so. Usually once a month.

Think of it as a tune up.

Making sure my orbit shots feed as cleanly to my flippers as possible is one of my big ones.
I hate it when a fast orbit shot comes down and hits the top of a slingshot instead of feeding cleanly to a flipper.

Lots of fine tuning including getting it playing fast with a great angle, lots of switch adjustments especially slings and pop bumpers (like mine sensitive and brutal), adjusting flippers , making outlanes tough but not to tough, make sure orbit shots return to flippers, kickouts smooth and ramps/wireforms are smooth as butter. Im forever tweaking things on my pins as things move and get worn and bent. I love a great playing pin brutal pin if u miss your shot.....

Lots of patience...... and what they said.

Small tweaks are always going to be necessary to keep any complex machine shuch as a pinball machine running smooth. Woodworkers often talk about dialing in their tools regularly to ensure smooth operation and a tablesaw is a much simpler machine. Even if it was dialed in at the factory, vibration etc from shipping is going to undo some of that.

For me it means making sure all switches and mechanisims are operating properly as well as making sure that everything is clean and properly secured. Then lots of playing to verify it feels good for you alibg with additional tweaks.

This. Once a game is completely functioning, and every feature working, it needs to be made fun and how the operator desires it. The overall feel, how "fast" a game plays, balance (one example is tweaking level because perhaps a ball consistently comes down a particular outlane, or SDTM off a ramp) adjusting details such as making a ball come smoothly into the flippers from the ball guides. Changing flipper rubbers for desirable bounce or control. Adjusting sensitivity of slings or pops for maximum effect. Adjusting plunger spring and angle for skill shots.

The list goes on and on...and all the details that make a game play good are adjusted through the process of a lot of playing.

I prefer to play "fly by wire" sure you can spend hours dialing in all the switches, filing your rails, superbanding everything and making sure there's not even a hair in your playfield...but why would you want to deprive yourself of all that time you could be playing the thing mon lol.

I don't think you can ever really have a list because every game is going to require different adjustments but getting the game leveled and angled right, adjusting switches, vuks, ball guides, etc. If something isn't playing exactly right I get creative if I have to with stoppers and washers or whatever I need to make sure it's playing how I like it.

I really like adjusting the pop bumper and slingshot switches so close that the ball just goes crazy bouncing around in the pops and if it barely hits a slingshot rubber it triggers.

In general, not inherently adjustable. Materials and guides vary. Simple wire guides can be adjusted by removing them and bending the wires where they insert into the playfield. Any screw in guide, try first loosening to see if some play can be found and retighten. Tougher cases can require more serious modification such as filing, or replacement if worn.

How do you do this exactly?
Is it by adjusting the pitch/level of the machine or something else?
My new WPT has the left orbit sending the ball STDM.

I don't know what game WPT is, but if the ball rides down a tall metal guide that directs the ball, see if there is a screw or post that holds the end closest to the flippers, loosen, move the metal piece closer to the side, then tighten the screw/post. See if that does it - a small adjustment makes a huge difference.

If that doesn't do it, then drastic measures are in order. This involves SLIGHTLY bending the metal piece so it doesn't push the ball out as far to the center of the playfield. I found that its easier to bend it near the end of the metal piece, and I use a pair of lineman's pliers with a rag so as not to scratch the metal. This ends up being trial and error - be patient. Of course, your results may vary. Note that I have only had to do this twice in all the years of fixing machines, so again, this is a drastic step, but it does work.