As full time or part-time bounty hunters identifying best bounties are very important since there is a tendency of increasing scam ICO''s now. Here I am giving some attention to following factors when choosing good bounties.
1. Rating- If the ICO has some rating. If this rating is good or high it is a indication that this is a good ICO.
2. Managers of the bounty- some managers has good reputation such as Amazix , Kripital etc.
3. The team behind the team -IF the team is strong and capable with good track record it is a indication that the bounty and ICO will succeed.
These are the main points come into my mind.
You may also want to consider if it is affiliated to credible bounty platforms or to some with bad reputations like tokensuite. The problems sometimes is not within the manager but for some reason there is a continuous trend of bounties from tokensuite that do not pay its participants so its best to avoid these scammers.