There are a few ways to increase your chance's of pick up:
Make sure your campaign budget hits your pitched publishers' minimum budget
Keep your CPC selection competitive: $2 in the US/AU, £1.50 in the UK
Stretch your campaign timings for more pickup opportunity
Load up your header with sale keywords, holidays, and brand highlights
Mix up your imagery with both product and lifestyle images
Target industry-relevant publishers so you know you’ll stick out to them
Don't put all your eggs in one basket – aim for 4-6 publishers for your best chance at pick up
Sweeten the deal with exclusive discount codes.