The most accurate planning is obviously done on the basis of experience in developing the same sort of support for systems. Planning should include the review and approval activities of the performance support developers of the software requirements and design documents, as well as the review and approval by software and user interface developers of performance support documents. When performance support is part of the software development organization, performance support project planning is closely tied to the software development plan. Analogy models are used to estimate the deliverable’s size, costs and/or development time, through comparison with one or more similar deliverables developed in a project. Successful planning for any project requires both a good planning process and appropriate tools. The use of estimation tools during planning and early design forces project managers to consider more carefully both the characteristics of the products they expect to deliver to the customer and the development environment.