You can relax at home with a cup of tea every bit as good as those brewed by experts in a tea shop, but it's not as simple as dunking a tea bag into a cup of boiling water. Start with fresh cold water, not the water left sploshing around at the bottom of your kettle. Boiled water begins to deoxygenate, so the second time it's used, you get a flatter-tasting tea. In that case, stop the kettle at the first signs of steam. If it does come to a full boil, then let it sit for 45 seconds to cool off slightly.
Darker teas steep longer.
Black teas, for instance, can steep for 4 minutes. When purchasing high quality teas, use the specific steeping times that are often provided with them. In general, the larger and darker the leaves, the longer the steeping time. To avoid a bitter flavor, remove the loose tea as soon as it's done steeping. There are several ways to steep leaves.