Preheating is a key element of successful brewing.
Not only should you always preheat your teapot, but there's even a trick that will prevent your teapot from suffering a thermal shock. Start by pouring the off the boil water on the lid of the closed teapot (see above). This safely increases the temperature of the teapot. Then, in a second step, remove the lid and pour the water in the teapot. Be especially cautious to do so in a cold room or with an older teapot that hasn't been used for a while.
I live in Taiwan since 1996 and have been studying tea with Teaparker. He's a worldwide tea expert and author of over 30 tea books. The study of tea isn't just theoretical, but it's also rooted in daily practice. It's a path of continuous improvement. As my brewing technique improves I get access to better teas and better accessories. These things go hand in hand. My blog documents my learning since 2004. And I have set up an online tea boutique with my selection of top quality teas, accessories and tea culture.