Just read at their whitepaper and do your own research about that program. Maybe it's hard at the first time, but eventually it will be easy for you to know the best Bounty or not.
Some bounty is not good and they are the bounties that are not lucky and we can say that it is wasting our time because of not getting payments from it,and if there is unlucky bounty,of course there is also good bounty and their projects is lucky and if we are lucky to choose them,we are also lucky to have them and we can get huge profit from it.by researching of the background of the campaign,that will be the right way to do to know if the bounty is trustable.