If you think about it, the majority of the drink that you're about to consume is actually water. That means that the kind of water you use is just as important as the beans themselves and can have just as strong an effect on the flavor outcome. Avoid tap water with a discernible taste, as well as softened and distilled water, which remove many of the essential minerals in water that you need for coffee brewing. Your best bet is bottled spring water or tap water with an activated charcoal or carbon filter installed.