I heard that some bounties fail to pay participants at the end of work. Considering this senerio, how can one know which bounty is a good to participate in?
It's hard for us to know which one is good for you to follow,
before we follow the bounty, you must first see the rules they apply, and what we have to do with the bounty that you will follow. Indeed there are some like you said, after following everything from the bounty they do not pay, or they pay but the token is not on the market aka coin scam.
So we must have a lot of patience in participating in each bounty, the name is a gift, maybe the gift they give to us bounty participants is very valuable or vice versa. This is where you need to be careful in choosing and following the bounty projects they offer.