At a point the team start given excuses to abide by what they promised to do or stop communicating with the community then I can sense the project is scam.
by that time it is already too late!
my criteria is when a project has one of these:
1. a premine of any size. this can be actual obvious premine or shadow premines which they try to hide it which is even worse.
2. any type of fund raising including but not limited to ICOs, IEOs, STOs,... because any project that asks for money up front is planning to take the money and abandon the project without an exception.
3. lack of innovation. a new cryptocurrency needs to be stand alone, NOT a copy of another project and it has to have some new innovative features in it. if it is rehashing the same ideas then it is planning to fail and run away.