You cannot improve what you don't measure. Google Analytics 4 (GA4), the current version of Google's free analytics tool, tracks how visitors find and use a website -- which pages they view, how long they stay, and which marketing channel referred them. Key performance indicators (KPIs) should be chosen based on the campaign goal: an awareness campaign might track reach and impressions, while a sales campaign tracks conversions and cost per acquisition. Return on investment (ROI) is calculated as (Revenue Generated minus Cost of Campaign) divided by Cost of Campaign, expressed as a percentage -- a campaign that generated ₦500,000 in sales from a ₦100,000 spend has a 400% ROI. Reviewing analytics regularly, not just at the end of a campaign, allows you to adjust underperforming ads or content while there's still time to improve results.