Cloud computing is starting to become real. I say that not because senior IT leaders at three of Computerworld's most recent conferences -- Premier 100, SaaScon and SNW -- couldn't stop talking about it, but because we're moving out of the "Why should I do this?" stage and into the "How can I do it?" phase.

What's more, the blind fervor is gone, replaced by healthy skepticism and active grappling with the frustratingly complex issues that need solving before CIOs will feel comfortable signing up with software-as-a-service, platform-as-a-service or infrastructure-as-a-service vendors. Many see the potential benefits of at least one of these cloud-based services for their organizations, but they need vendors to clear a number of hurdles before they will seriously consider adopting services-based IT.

 Options include public clouds and external private clouds. Here's how to choose wisely.