How Do Clouds Form?

As someone who loves looking at clouds, and may have a somewhat scientifically directed brain, I'm fascinated by the shapes and structures of clouds. Where I live, at the foot of the Rocky Mountains, provides endless examples of them. I write about them a lot, but I don't think I've ever explained just how clouds form. After all, it's a little weird: A typical storm cloud can have a mass of millions of tons, yet they float! I know this is because they're less dense than air, but that still seems...