There is no proven formula, but getting familiar with the project and the people behind is always a good start. Take your time, explore other ones and give it a space to show if it is a legit project or just another scam. Go in as first as a researcher, later as a bounty seeker or investor.
If you wanna understand smth about the project you have to spend much time on learning it. It doesn't mean reading and checking social networks are enough, you have to monitor its activity during 2-3 weeks. It won't guarantee anything but will raise your chances of success very much!