The most important concept in the art of making teapots is 'Shui Pin', 水平. The original meaning is 'water level', as in the tool, but in teapot terms, it is the three point line connecting the tip of the spout, the rim of the teapot's opening, and the vertex of the handle. In terms of function, a pot with good Shui Pin is well balanced when held and pours comfortably. Because of shrinkage of the clay during firing, you can judge a potter's expertise by their ability to produce a nice Shui Pin.
For the first Yixing teapot I ever bought, the tea master at Kkikdageo chose a simple, standard looking pot, which he said was as a good teapot for a beginner. It turns out its Chinese name, 'Biao Zhun' 標準, translates directly as 'standard'. It's an old Early Republic of China Shui Pin design that the Yixing No 1 Factory literally standardized and produced in mass quantity during the 1960's. The highly functional design of the Biao Zhun Shui Pin pots has kept them the standard design. Though different specialized teapots have been designed for different teas, a Biao Zhun Shui Pin is suitable for any tea.
A quick way to check a pot's Shui Pin line is to remove the lid and set it upside down on a flat surface. If the spout, rim, and handle are all touching the surface, then you have a well crafted teapot. Another test is to set the lid so that it is balanced either between the rim and the spout or the rim and the handle. This can be useful when allowing the steam to escape, not to cook the tea, or when leaving the teapot open for drying. To demonstrate this, I've superimposed two photos, with the lid balance on each side.
