I think you should search for bounty campaigns published on the forum by high-rank users with a good reputation, there is a big variety of bounties so it may be a hard task to pick one so just let yourself go at first for the reputation.
Picking up the best signature campaign is very simple if you spend a lot of time in this forum it will the way to get a good signature campaign there is no other way to find the best if you spend lot of time on something it will give the response to that this is my opinion.