Two Factors: Time and Temperature

Suggested ratio is one teaspoon of leaves per cup of water. However, the light and voluminous teas will taste best with twice that. To steep, please use boiling water (100°C) when preparing black, dark oolong and herbal teas. And it's important to use cooler (80°C) water when steeping green, light oolong and white teas. And remember to not over-steep, or your tea will taste bitter. Rule of thumb is 5 min. for most black, 7 min. for dark oolong and white, and only 3 min. for light oolong and green teas.