• Check all you can find in their Bounty Thread
• TEAM's background info
• ICO's Aim or Goal
• Read Whitepaper
• Do research on their ICO
• Research first if their project will be useful or not
• Active Bounty Manager.
• Join bounties that's been manage by successful bounty manager from previous managed ICOs
Example Team is Amazix that has managed lots of successful bounty campaigns.

Or you can check the threads provided by: