Creating the business case refers to the process of actually putting some numbers down as to the value of the SOA to the enterprise or business. This means looking at the existing issues (from the previous step), and putting dollar figures next to them. For instance, how much are these limitations costing the business, and how does that affect the bottom line? Then, how will the addition of SOA affect the business -- positively or negatively?
Put numbers next to the core values of reuse and agility. You'll find that agility is the most difficult concept to define, but it has the most value for those who are building a SOA. Then, if the ROI for the SOA is worth the money and the effort, you move forward. This tactic communicates a clear set of objectives for the effort, and links the technical notion of SOA with the business.
The deliverable for this business case should be a spreadsheet of figures, a presentation for the executives, and a report for anyone who could not attend those meetings. Keep in mind you'll see this business case again, so be conservative but accurate.
Creating the execution plan refers to the detailed plan that defines what will be done, when, by what resources, and how long. This is, at its core, a project plan, but most people will find that the systemic nature of SOA requires that a great deal of resources work together to drive toward the end state. Leveraging and managing those resources is somewhat complex, as is the project management aspect of SOA.
Delivering the goods means just doing what you said you would do. Execution is where most SOAs fall down. However, if you fail to deliver on-time and on-budget, chances are your SOA efforts won't continue to have credibility within the enterprise and future selling will be impossible. So, say what you'll do, and do what you say.
Selling SOA is somewhat more of an art form than a well-defined process. It requires a certain degree of understanding the big picture, including the technology, the business, and the culture of the enterprise. More important, the sale needs to be followed up with delivering the value of the SOA. That's the tough part. What works so well in PowerPoint is a tad more difficult in real life.