1. Trusted developers.
2. Good road map
3. White paper is realistic
4. There is something that they'll support for the usage of that coin
5. Long term plans
6. Good marketing
But those are all the thing that influnce an ICO trustworthiness. What makes you tick, what triggers the feeling that you have to take part in that ICO?
Maybe the last investment can help you understand what affected you.
Yes trustworthiness is what an investor get into in an ICO. Maybe you can try to read again what I said because it's clear that it's on my number 1 list. When they have trusted developers the project will be trustworthy because those devs are experience to run a good project and ICO. They are not just crowdfunding and will runaway after funding that project by many investors.