Although it can be one of the most expensive teas, quality varies widely in the marketplace. There are many varieties and they are determined by both the roasting level and harvest time. Lightly roasted Tie Guan Yin is "green" tasting whereas a darker roasted version will develop a more nutty quality. New spring harvests are usually the highest in quality. Aged Tie Guan Yin has become popular in recent years. The oldest that I've taste so far was 20 years old.
This tea lends itself well to traditional gongfu style brewing but it can also be brewed easily in a western style teapot. It can stand up well to heat pretty well so your water temperature will usually be between 195 and 212 degrees. I prefer to do 30 second steepings using a gaiwan. If using a teapot you'll want to let the tea brew for 3 to 5 minutes.