You can increase your stamina in Genshin Impact by upgrade the Statue of The Seven, using Anemo Elemental Resonance and character passive skills like with Kaeya.
1. Upgrade Statue of The Seven
Alright this one is probably obvious to you. But in case you are new, Anemoculus and Geoculus are used to upgrade your Statue of The Seven which in turn upgrades your stamina pool.
2. Use Kaeya
Kaeya’s passive skill Hidden Strength decreases sprinting stamina consumption by 20%.
He is a free character available very early on. You don’t need to invest in upgrading him either. The passive is available as soon as you unlock him.
Just add him to your party and you will receive the passive.
3. Anemo Elemental Resonance
Having two Anemo (Wind) element characters in your party activates the Impetuous Winds Elemental Resonance effect.
It decreases stamina consumption by 15% and increases movement speed by 10%. Aditionally it also shortens Skill CD by 5%.
There are also foods that can restore stamina/reduce stamina consumption. However you may want to save them for battles.