Is it bigger than a breadbox?
To get a quick feel for how big the project is, run the planning process at coarse resolution.
Let's say you're the only one on the project so far. What's the first step? How can you use shopping to bring a project into existence?
Items—. Big stories
Prices—. Rough estimates of the time to implement each story
Budget—. Roughly how many people you have to work on the project
Constraints—. Supplied by someone with business knowledge
The purpose of this first plan is to quickly answer the question "Does the project make any sense at all?" Often these sanity plans are made before there are any technical people on the project at all. Don't worry about getting perfect numbers. ...