3. How are my apps and data protected from other users on the same cloud servers? Don't make any assumptions about how vendors handle multiple users, also known as multi-tenants, on the same cloud servers, Claybrook says. Ask detailed questions about the extent to which your data and apps will be protected when running with those of other cloud customers. Claybrook recommends having each vendor show you how they segregate their customers' data and applications.

4. Can I speak with some of your customers? Claybrook recommends asking for customer references. Speaking with customers will give you the opportunity to compare what the vendor has told you with actual customer experiences, he says.

5. Can I move an existing app from my private cloud to your public cloud without massive reconfiguration? This question is critical because your cloud vendor's infrastructure is likely completely different from yours, Claybrook says. Consequently, if you want to move an app out of your datacenter, there will likely be some conflicts. "The application has been built assuming the use of particular storage technologies, specific network configurations and specific management tools," says Claybrook. "You need to know if it's moved to a public cloud, where all of those things are probably different, how you can make it work."

The vendor may provide tools that can make the migration go more smoothly, Claybrook adds. It also helps to find a vendor whose technology ecosystem is similar to yours. "Some cloud vendors support multiple databases and various forms of networking," says Claybrook. "You'll want your applications to perform at least as well in the cloud after it's moved as it ran in your datacenter."

6. How do I get my data back? In the event you need to move your applications and data back into your data center (or to another cloud vendor), you need to know exactly where your data is stored and how to get it back, Claybrook says. You also need to be clear on your contractual obligations should you ever decide to terminate the relationship with the cloud vendor. For instance, you may owe the cloud vendor money if you terminate the contract, he adds.