I usually trust good bounty managers + projects which have a clear and concrete roadmap.
There are so many bounty that you can choose to join all we need to do is to check out its capability of handling the campaign. Its very important that we know the details of the project and how it run in the market.
For now many bounty campaigns are ongoing some of them are trusted, scams and some of them are failed, that is why It's very hard to select a bounty program, even if how good the bounty manager. Research and read the whitepaper of the project so that we don't need to invest our efforts and time for nothing.