You must have plenty of experience and knowledge so you can make your choice. Check the project's whitepaper, team, concept, roadmap. This factors could showing you if the project is promising or not, i think you need to choose bounty campaign with big bounty allocation, limited number of participation and/or managed by good bounty manager. If you don't want to read the whitepaper at least read their one pager and the team's background. Except if you're investor then read the whitepaper is a must.