The Top Conversion Paths report is a great tool to understand how visitors find your website before making a purchase.

Google Analytics -> Conversions -> Multi-Channel Funnels -> Top Conversion Paths

The standard overview groups traffic into broad source categories like “Paid Search”, “Direct”, “Referral”, “Organic Search” etc. In the example below you can see that the most common conversion path consists of 2 paid searches before people make a purchase.

Click on “Secondary dimension”, type in “campaign” and select “Campaign (Or Source/Medium) Path”.

This will generate a more detailed report, showing exactly which Adwords campaigns or other campaigns led to a conversion.