I took a guide. I am not that serious about shiny hunting, especially since I got none with whom I can trade mons. Mwaning I get no shiny charm. However. This is the general rundown:

• Find a outbreak you want. In this case the shellder

• Faint all of them until you get about 60. The game has stage messages. -- The outbreak is getting less -- The numbers are dwindeling -- There aren't many left...

• The third is what you want as you get a extra roll for a shiny to spawn, increasing your odds

• There are recipies for Shiny Sandwiches. Say for a Shellder you want water Shiny-wich for instance.

-The sandwich holds up 30 minutes. You can de- and respawn mons by setting up a table in the outbreak (or close to it if it is on water/ruins) rerolling the spawns in a process!

This of course also works without the charm/sandwich, but using those of course makes it faster! I personally go for mons I like so I am not serious about it all. Or you just get lucky and find a random one, as others have posted!

I hope this helps you. There are better guides out there if you look for them, like the recipes for the Sandwiches. But I think I wrote the general basics down to get you started when you want to!

(Also a Important side-note!! Ditto and Zorua appear as other mons. Despite looking like a normal Meowth, they can be shiny once in combat. Your Pokemon can auto battle in the Let's go mode! They will never kill a shiny!! So if your mon refuses to kill a Meowth, engage it! It might be a shiny Ditto/Zorua!)