Look For Koroks
The cute woodland creatures from Wind Waker known as Koroks return in Breath of the Wild, and you’ll be seeing a lot of them. There’s a whopping 900 of these little guys scattered around the word, and each time you find one, you’ll be rewarded with a Korok Seed. These can then, in turn, be exchanged to upgrade the number of inventory slots you have.
Koroks can mostly be found around trees and wooded areas, but also scattered around other places like under rocks. More often than not you’ll also have to solve a small puzzle to find them, like moving metal boxes around or recognizing a pattern. You’ll definitely want to carry more equipment with you, however, so always be on the lookout for a Korok. With so many packed into Breath of the Wild, you’re bound to just stumble on a few anyway.