During your adventure in the world of Teyvat in Genshin Impact, you will need to get resources be it for quests or to upgrade your weapons and characters. The in-game map already have markers you can place on the map to display farming spots on the mini-map.
To do this, you either have to spend your time researching on your own or use an interactive map. miHoYo even has you covered as they introduced their own interactive map.
The miHoYo interactive map
- Map link
This official map is convenient because you can be sure it's up to date and changes regularly when new spots are added like with the release of Inazuma. You can even select the fishing spots.
You can also create routes for your farming sessions and make sure you don't waste time zooming in and out of the map too much.