Ask pointed and direct questions. Ask about earnings. Ask for any form of proof or documentation. They will avoid the questions like the plague. It never fails and it certainly has been proven on this site once again.
Remember that these MLMers are primarily out to recruit more suckers into their evil web of lies and deceit, so it doesn't bother them to post their entire life story all over the internet with their contact information. Yet when you bring up their personal lives, they will scurry like the cockroaches they are. That's been proven on this site once again also. My heart truly bleeds for these poor little sensitive and delicate flowers. They just can't grasp that they're the ones that put the information out there for everyone in the world to see and easily find. They will comment about their plans, their family, their jobs, just about everything that's not related to the MLM. But it's not their fault and we certainly have no right to question or doubt them, right?