First thing is you have to know what is in the water you are using. This means you either need to start with Distilled or Reverse Osmosis water.... or, send your tap water into Ward Labs to get it analyzed (this is what a lot of us have done). It is easy, quick, reliable and pretty cheap.
Once you know what you are working with, software like B'run Water is one of the best ways to work with your water and adjust for certain styles.
Go to the "Brewing Science" subforum and check out the water chemistry primer in the sticky section at the top. That gives a real basic way to get started using Reverse Osmosis water and some simple water additions. The Brewing science subforum is the best place to find water information.
