It starts by not advertising a service you don't trust. And if you do trust it, you can just use it. Why would you recommend others to use something you wouldn't trust with your own money?
Makes sense. For this reason I used and tested the service myself a few times mixing my own sats. Also for this reason I didn’t rush to withdraw all my weekly signature gains. I left those in the “mining campaign”, and not only for the 12%, but just because I wanted to “believe” in the service I was advertising.
I tend to believe in the services I advertise, this is my rule. Even if I think signature wearer have by no mean any responsibility if the advertised service turns out to be fraudulent.