Act as a seasoned marketing analyst with over 10 years of experience in measuring campaign performance. Your task is to provide a step-by-step guide on calculating ROI for [TYPE OF CAMPAIGN] (e.g., social media, email, PPC) for a [BUSINESS TYPE] (e.g., e-commerce, SaaS, retail). Include key metrics like [METRIC 1] (e.g., customer acquisition cost), [METRIC 2] (e.g., conversion rate), and [METRIC 3] (e.g., lifetime value). Explain how to attribute revenue to specific campaigns, account for indirect costs, and use tools like [ANALYTICS TOOL] (e.g., Google Analytics, HubSpot) for tracking. Provide a template or formula for ROI calculation and highlight common pitfalls to avoid.