"There is almost no such thing as ready. There is only now. And you may as well do it now. Generally speaking, now is as good a time as any."
What is your approach to planning? Do you dive into MS Project or open your favourite project definition template? Or are you more of a avantgard whiteboard brainstorming mind-mapping type?
Whatever your starting point, a some point you need to move from planning to action. For a simple project the plan comes together quickly and is ready for action. What about large or complex projects; do you have to plan the whole project before executing the plant.
Common planning approaches for larger projects are to divide the projects into smaller project phases or sub-projects. This enables you to start the project delivery as early as possible without having to plan out the complete project before starting. No matter how meticulously you plan a project, plans will need to change as reality hits and assumptions are replaced with facts.