Follow credible bounty managers. Mostly, startups rely on bounty managers with enough experience in marketing and handling of bounty hunters. You can check them out via telegram and bitcointalk. Been tailing some bounty managers and teams who has handled great projects.
bounty managers are being paid to manage the marketing of the ICO.
They are credible because they handled many ICO before when scam is not in the market?
To have a good bounty you should look for the ICO itself and the project!
Remember, Bounty is based to the success of an ICO.