Brewing a good cup of coffee starts with good coffee. Coffee brewing is the extraction of water soluble flavor compounds; good technique will ensure a proper extraction, however, if the flavor compounds are not good to start with the brew will still not taste good. There is quite a bit to unpack in selecting a quality coffee...

Next, utilizing good filtered water allows you to taste the flavor extracted from the coffee, instead of chemicals or chlorine tastes that municipal water may impart. Water chemistry is a deep subject on its own - involving starting from a base of reverse-osmosis or distilled water - and measuring individual mineral components - to achieve the ideal balance of the impact those minerals have on taste. A great place to start would be purchasing purified drinking water frrom a store, or at least filtered water from a refridgerator - moving up into home reverse osmosis systems. Testing various water sources will help you identify what you like or dislike about a particular water source.