Conducting a feasibility study.
Measuring the available and/or attainable resources against the due activities.
Calculating or estimating costs.
Drawing up a budget.
Drafting the Work Breakdown Structure.
Outlining the scope of the project.
From there you should:
Conduct a SWOT analysis.
Do environmental scanning.
Identify macro environmental factors directly affecting the project.
Make assumptions and prepare for differences (outcome vs. Initial estimate)
Come up with a contingency plan or strategy, in case the original project does not succeed.