Just pick a signature campaign where the team doesn't look suspiciously scam. That's what I do but somehow I end up with a scam team
I join a campaign because I think the project can be good but if it don't work well, I wouldn't be blaming because I picked up a wrong project to promote its just that the team are incompetent. I think the best tips from me to choose bounty is look from the team behind and what project it is, because the best project is always have good team behind, i prefer join in trusted team like amazix team, because from them the percentage of success is high so I fell more secure in bounty
The success of the project is also your success. If for example the ICO didn't get the softcap, you as a participant ain't getting paid. That's the reality.