The Google Display Network
When it comes to a direct return on your investment – in the vast majority of cases, the Google Search Network will easily beat the Google Display Network.
But that is not to say that the Display network is never worth using.
With that in mind – here are some pre-recorded webinars by Google that will be of interest if you want to use it for Branding or Re-Targeting/Re-Marketing (and perhaps even *sometimes* for getting a great direct return on your investment):-
Creating Effective GDN Campaigns:
Advanced Optimization Techniques:
Remarketing on the GDN: