Usually, a simple google search regarding the ICO, will help you find out if it's scam or not. Just google "[ICO NAME] scam" and there will be either no result or you will find out the ICO is actually scam.
Not always, but very very often ICOs became fraud only once, and totally
So it can be hard to identify some scam before it turns out scam, thats the point.And sometimes google cant help with this decision. Thats why all of us need to make their own research. We cant get clear market until people stop investing scam projects.