Joseki is the standard corner play that is considered good for both black and white. There are 4 things to know about Joseki:
1. Know the order of playing Joseki
2. Have a wide variety/knowledge of many Joseki, making more choices in actual games.
3. Eye Space is important for Joseki, play Joseki by keeping in mind two places for Eye Space, the corner and edge.
4. Direction is important. Direction in the sense of where the stones expand to.
1. The important of the Edge
In the opening, both players aim to expand towards the edge, hence the center of the edge becomes priority.
2. Attack vs Defense
A stone is most valued when it came both attack and defend.
Move is good, it attacks the two white stones and at the same time defends the weakness in the corner.