All of the truly important decisions happen during the first stage of a project; it is when the grounds for success (or lack of) are laid. Consequently it pays to take it slow, even when the realities of life and business suggest otherwise.
One of the most critical – and often most challenging – tasks at this stage is for the project manager to engage openly and effectively with all stakeholder groups. This engagement must result in clear commitment to inputs required and defined outcomes.
Beware: of making assumptions and failing to ask the difficult questions at this stage.