1. CHECK THE PROJECT - you need to do research about the bounty, the project team, the whitepaper because some might just copy and paste it, the advisors, roadmap, bounty pool and ofcourse the founder you need to be a good observer, check their background because sometimes by just merely observing and reading you will know right away if the bounty is a scam.
you are correct, the problem that we have and that people know that project X is not good quality, does not show some seriousness and even with many red flags these people still insist on participating bounty
2. CAMPAIGN MANAGER - the one that you should always consider, because if the bounty manager is scammer then the bounties itself is a scam, and it is really obvious if the bounty manager has a negative trust then surely he or she is scammer, one thing to consider also is the rank of the bounty manager the higher the rank the higher the legit factor, you can always do research here there are many list of legit and reliable bounty manager and the list of all bounty manager scammers.
you should do your own research and the fact that the bounty manager is on some project does not mean that the bounty manager has some power to ensure that the project is legitimate and will not become scam unless in some cases the bounty manager knows the project is scam and still remains bounty manager, but overall the bounty manager is not a member of the project team, he can also be deceived.