It's an obvious thing that you should do your own research, investigate the subject. You should check the team, the social networks and community, the idea itself, you shouldn't think that some exchange's listings can be a guarantee of your profit. The market has only few good projects annually so that it's really hard to find the worthy ones.
Indeed but lets admit that some of us are lazy to conduct a research and verify if the claim of the team were true, what matter is the profit and its because of greed. If the offer is too good and promising high return and saying they will be listed in reputable exchanges, think and verify it first to make sure they are not fooling around for their own sake.
Except laziness many of us are not equipped with technical knowledge. I participated in one bounty last year
where everything looked fine, their site, their WP, their team was active on social networks. With my research
I thought they are a great project. Before the end of ICO they just went offline everywhere and nobody saw
them again.
Now when I doubt in new projects even if everything look perfect. Often I decide to invest in well-known
alt-coins than in new projects just because of my bad experience.