'Cloud' is becoming mainstream, but the know how on best practices amongst architects/developers is not widespread. The approach one takes is the single most factor that decides success or failure. There are significant # of aspects one needs to know before taking the first step of migration or hosting in the cloud.
A few months back as part of 'Architect Roundtables', we had tabled the same very topic and the discussions were great. In the last few weeks, a colleague of mine (Srikantan) and I managed to put together our thoughts in the form of an article.'Open Source for You' magazine (print and online) found it worthy of publishing for the larger benefit of cloud practitioners.
If you are an Architect (or even a developer), and considering Cloud, below should be a good start.
"A Practitioners Guide to Moving to the Cloud"
PS: Our intent it to make it an exhaustive collation. If you think we should add any particular guideline, please leave you comment and will be happy to consider.