>>35197458It's going to be easier in Sun. The Shiny Charm is easier to get; you only have to get 300 Pokemon (or 400 in USUM) vs. in ORAS where you need to complete the National Dex.
First, you have to pick a Pokemon you want. Then you have to choose what method of getting it you can use in your game. Take into consideration what Pokemon you might need to help you out, and what items you'll need. There are a few different methods for Sun:
>Random encounters: straightforwardly encountering Pokemon until you find a shiny.>Soft reset: put yourself in a position where you encounter a Pokemon and reset until you get a shiny.>SOS chaining: when wild Pokemon call for help, the Pokemon that are called in have a higher chance of being shiny. After 30, your odds of finding a shiny are 1 in 315, or 1 in 273 with the shiny charm. The odds reset after 255, but they don't reset in USUM until you break the chain.>Masuda Method: breed two Pokemon from different regions (say, an American Litten with a Japanese Ditto).Also consider any problems that might fuck things up. For example, wild Geodude know Self Destruct, so you'd need a Pokemon with the ability Damp to SOS. Salandit has a 1/8 chance of being female, so if you want a shiny Salazzle, you need a male Pokemon with cute charm on the field. That sort of thing.
Once you have everything you need, go for it, and don't stop til you get it.