Any Strategy must be capable of execution and so the first priority, is to establish a Cloud Strategy
Team, usually driven by the CIO it will consist of your IT people and the vendor you select. It is important that your organisations business operations also have input into the strategy and they should be in areas such as Finance, HR and Sales & Marketing.
Each application will need to be analysed to determine the best fit for its hosting environment. If the workload is to be retired or no longer receive further investment. You will need to investigate whether to host the application workload on a Public Cloud (such as Azure) and if not, will stay in an on-premises or in a private cloud. If the workload could be placed on an IaaS cloud environment, would it be a candidate for migration to obtain benefits of cost reduction. Below shows the mechanics of this analysis. A similar approach is taken for SaaS and PaaS.