1.   The team working behind the ICO properly. Investors carefully check the qualification, expertise, skills and experience of the team members.
2.   What is the project? The idea behind the project should be new and interesting.
3.   Investors read the whitepaper very carefully so it must contain all the important details about the project.
4.   Investors also look after the goals. But goals must be realistic as unusually high goals point towards scams.