The firs, you can find bounty at here:
https://bitcointalk.org/index.php?board=238.0A good bounty program means a good project and vice versa (mostly).
Find out about their community (East or Little), their team (real or fake), practical application.
If community east real team, they have a team who have known in the Crypto you be confident that as their bounty.
If the community is large, the team is real, the team they have the reputation in the Crypto world, then you confidently participate in their bounty program.