It is difficult to answer this question. But I adhere to some rules for myself.
1. How smartly the smart contract was created
2. Openness of the company, they do not hide behind a screen of the Internet.
3. Ratings, as a rule in rating sites appear worthy candidates.
There are a number of rules, but these are already enough that a beginner has entered the course of the matter and did not lose too much money for bad ICO