When you're first learning how to brew tea, it can be easy to overlook ideal tea brewing times (or to simply forget when the time comes to stop brewing). Over-brewing can easily ruin an otherwise perfect pot of tea. Under-brewing, while not as serious of a problem, can also result in sub-par tea. Whether you're using a clock, a timer (such as the TasteTimer iPhone app) or simply counting in your head, brew times shouldn't be overlooked. The specifics vary for each individual tea and brewing method, but this guide can help you get on the path to brewing great tea.
General Brewing Notes
Starting with your supplier's brewing instructions is generally a good option. Try them and see what you think. If you're not satisfied (or you just want to take the tea for the brewing equivalent of an all-terrain test drive), try varying the water to tea ratio, the brewing temperature and/or the brewing time.
If your tea tastes unpleasantly bitter or harsh, reduce the brewing time (and possibly also the temperature).
If your tea lacks nuance and complexity, it may be an issue of the brewing time being too short or long, but it's more likely an issue of brew temperature or water to leaf ratio (not enough leaves for the amount of water you're using).
If you prefer your tea strong, don't brew it for extra time. This will make it bitter. Instead, add more tealeaves to your brew.
Above all, follow your taste buds! If you prefer your Gyokuro green tea brewed for four minutes instead of 30 seconds, then (although it's not something I'd recommend) it's completely up to you.
The instructions below are for brewing Western-style, not gong fu cha or brewing in a gaiwan.
How to Brew White Tea
White tea has a huge range of brewing times. Some people only brew it for around two minutes. Those who prefer a much stronger taste may brew it up to seven minutes. Personally, I think around four minutes is usually a good time -- but it depends on the tea.
How to Brew Japanese / Steamed Green Tea
Japanese steamed green teas require very short infusions. Most are best at between 30 seconds and two minutes. If you're reinfusing your leaves (brewing them more than once), some Japanese green teas actually brew better with an even shorter infusion (such as 15 or 20 seconds) the second time around.
How to Brew Chinese (Roasted / Fired) Green Tea
Most roasted/fired green teas are best when brewed two to three minutes. Some can handle four minutes.
How to Brew Oolong Tea
Oolongs vary quite a bit in terms of their flavor profiles and their shapes, so their brewing times also vary quite a bit. Some require as little as 30 seconds. Others can be brewed for seven minutes. I generally recommend following your tea supplier's instructions, or testing oolongs at around three minutes.
How to Brew Black Tea
Most black teas are ideal when brewed between three and five minutes. Darjeelings (especially First Flush Darjeelings) and some Nepalese teas are better with two- to three-minute infusions. If you're adding milk and sugar to your tea, you may want to brew it a little longer.
How to Brew Pu-erh Tea
Pu-erh newbies may want to brew for one to two minutes. More seasoned pu-erh drinkers (and coffee drinkers) may prefer their pu-erh brewed for five or six minutes.
How to Brew Herbal Teas
Tisanes or "herbal teas" come from many different types of plants, so they require many different brew times. Try using your supplier's instructions as a starting point for brewing, and then follow your taste buds, or check out these detailed herbal tea recipes.