You can download Bru'n Water calculator or stick with EZ Water calculator and just try to keep you're minerals on the lower end of the spectrum for the style you're brewing. If you need to tweak it to keep your pH good, you can. If you have to approach the high end of the mineral spectrum just to get your pH correct then you need to consider acidifying instead of raising the mineral levels too high. This is just my opinion on the matter. There are people in this thread that are very experienced when it comes to water chemistry, so they might have better advice. If I was in your shoes (which I was when I first started messing with my water) I would start the way I described above. I don't want to discourage you, but you might not hit it perfectly your first time. All things get better with experience..