Define the relevant industry:
Identify the participants and segment them into groups, if appropriate:
Assess the underlying drivers of each competitive force to determine which forces are strong and which are weak and why.
Determine overall industry structure, and test the analysis for consistency:
Analyze recent and likely future changes in each force, both positive and negative.
Identify aspects of industry structure that might be influenced by competitors, by new entrants, or by your company.
(Source: Porter, Michael E. "The Five Competitive Forces That Shape Strategy." Harvard Business Review 86.1 (2008): 78-93)