Funny how my takeaway (as someone completely removed from the action) has been the opposite: don't trust the tech, filter for trustworthy people. Time and time again we are shown that tech is not solving the human problem of greed and malice, and some kinds of tech rather amplify it.
By iterated experimentation, mostly. Social relations are a skill built on give-and-take actions on all levels, from the trivial chit-chat to lifetime friendships.
Look for signals and be skeptical I guess. Watch for over-promising. For someone giving advice, try to imagine how they could be paid or gain from selling you on this, or whether they could be influenced by people who do. For someone offering to take your money, do due diligence, look for track record and whether they make legal recourse early available. For example, transacting in cash or something similarly attractive to money launderers could be a red flag. (And yes 98% of subject industry should probably not be trusted so your filter has to be really selective.)
Make sure they have skin in the game[1], make sure they know they have skin in the game, and trust them with big things only if they have a good track record with smaller ones.
[1] In the case of dealing with money, 'go to prison if they steal it' does a pretty good job of filtering out the most common hucksters.
