Define the goals, target audience, budget.
Before starting a project, I like to plan everything to make sure we're on the same page and we can work hand in hand efficiently.
I always start a project with a lot of research to understand the market, see what has already been done, and stand out from the other projects.
I take a moment to sketch, talk with people, inspire myself from art/nature/books/shops/internet.
And it's the best step.
I try different propositions, read the brief again - try different concepts - again, redefine my ideas, try different concepts. Yes, again.
After working on several concepts, we can chose the one and have a g*ddamn good project.