Be careful with the automated rules to exclude, make sure you've had enough traffic from a domain (or page) to know if it's no good for conversions, some placements can surprise you. Sometimes a domain can look horrid overall, but pages within it can be excellent - you've got to figure out the point of diminishing returns - how much work you want to do slicing and dicing at domain level, or page level.
If branding is clearly wrong, kill it.
Mobile apps are notorious for poor conversions, AdWords has a special "catch all" exclusion "trick" to block mobile apps, see bullet3 point #3 here:
[
support.google.com...]
("If you don’t want your ad to appear in apps, it’s easy to exclude mobile apps from your placements. Just paste "adsenseformobileapps.com" in the “Placements” section of “Campaign Exclusions” from the Display Network tab.")
Make sure you use the category exclusions as well, scroll to bottom of placements screen, you'll see the controls down there.
Most definitely split Search and Display, they behave differently.
People using mobile for GDN, also might be something you want to suppress, segment by device to figure out how much, or to go to -100% bid modifier. If you have enough Conversions, the Conversion Optimizer, or Display Conversion Optimizer can help tame Mobile, and other slices of lesser performing traffic.
Look at the audience reporting, it can be useful to kill large swaths of placements by topic or audience - sometimes it helps to add Audiences (without a bid) so you can get Audience level stats, to allow data driven decision making at the segmenting level.
The gender and age stats, same thing - watch their reporting, see what the specifics say for your particular campaigns.
As before, let the keywords largely flow - their fungibility makes them far less useful for exclusionary segmentation - think of them in the positive targeting sense only, not so good on the neg side.
Remarketing is a complex beast, details too many to cover here - but consider adding Remarketing audience, again without a bid, to see if people who have already been to your site (or have already bought), should be bid up, down, or maybe even off - it really depends on the nature of what you sell (one off, or LTV type setup).
Use Analytics to review "Conversions | Multi-Channel Funnels | Assisted Conversions"... GDN / Display clicks are often early funnel touches, so your normal attribution may under report and therefore under value them - last-in can trick you into thinking Display isn't converting.
Got all that? Hahaha!
And, one more thing, have fun!
:-)
