A good cup of Chinese tea is divine. It is achieved through both premium tea quality and careful preparation.
Poor tea preparation can significantly reduce the quality of the tea brew in the cup. Caution is particularly important when brewing the premium quality loose teas as all teas are made of various stages of the tea leaves, gone through various degrees of fermentation and processed by various sets of skills.
For example, over steeping green teas by applying a lid during brewing can induce a bitter taste to the tea brew; insufficient rinsing of aged pu-erh teas can leave a dusty taste; soaking of any premium teas will diminish its refreshing taste; and too hot water can break down certain young leaves etc.
Preparation methods differ between tea categories and tea varieties within a category. Instructions here serve as a guideline.
With time and experience, you as a tea drinker will develop your own tea preparation technique and preferences such as tea vessels, tea types and flavours, tea strength and brewing time etc.