Well it is better to invest in a company/project that already has a function or working product. Most of the ICO got only a nice whitepaper and idea. Search also about the persons in the team and discuss it in the Bitcointalk forum.
well , it is not easy to manage the scam because most of all scammers are professional in doing salestalk. they do all the good words just to scam people. and one of the way to avoid the scam is to not trust at all about your buyer/seller. do some research because not small amount are in . but big amount of money are involved in this. so make survey and research. this is the best way to do.