you can earn quite some good money by doing bounties, but as you've said it's not always easy or obvious which project will succeed and which won't. What you can search for are projects that you genuinely like and projects that you would invest your own money in (if you were to). Try to follow the approach as though you're an investor and are looking for ICO's to invest your money in, you are investing in some way because you're investing your precious time, so you should be taking it just as serious in terms of researching about the project, reading the whitepaper and generally learning anything there is to learn about its technology, the industry and customers it is going to target. A combinations of all of these are what will help you determine whether a project will pay off or not.