How do I track marketing influence and Lead Source to Opportunities?

Hey Salesforce nerds: How do I track marketing influence and Lead Source to Opportunities?

How do I track marketing influence and Lead Source to Opportunities?

We use Lead Source to track where a lead came from (usually from marketing activities: site- whitepaper- event- webinar- contact form- etc.). When a lead is converted to a Contact it inherits the lead source. When an Opportunity is created we want to be able to report on the marketing activities …