There are a couple of ways to do it, but there are no automated ways, which seems to be what you want. The first way is to listen very carefully over a good monitoring system in a good sounding room and adjust the volume of each mix until it is at the level you want. The other option, also called "mastering" is to pay somebody else to do it for you.
Other people may tell you to "normalize" everything to a preset level, but if you do that you'll find out why shortcuts always come up short in audio recording: they may be the same level, but they won't sound good. You'll find yourself wishing some songs were quieter and some were louder, and there you are back on square one.
A rock ballad, a rocker and a ballad all require different levels, and the only way to find out is to do your mixes, burn a CD, and listen -- preferably on several different systems. Then you'll have an educated base to start from.
It's a good exercise in training your ears. In my experience, it won't happen the first time you try it. But recording is all about being meticulous, and this ain't a bad place to start.