What Makes You Trust a New PPC Network?

I'm looking at a few PPC networks I have not used before, but it’s hard to know which ones are actually reliable. I don’t want to judge a network only by CPC or traffic volume. Things like reporting, traffic quality, support, payment history, and campaign controls also seem important. For those who have tested new networks before, what made you feel comfortable putting more budget into one?
Would be useful to hear what you normally check first.

I normally test the same offer on a few networks. After comparing the actual conversions, it becomes easier to see which source is worth keeping.

If it's totally new, they are surely offering a trial to check their traffic quality. Even a most complicated panel with everything can't get much users without offering a test service.