If you askin about how to find scam coins, it's simple to answer, check website and development team, and also you must check whitepaper before that, but sometimes they are very close with trusted project, but there are always have a gap!
It's not easy as you say, finding a coin scam is very difficult for us to detect because they also commit crimes very carefully, even they are able to fake the team and their Whitepaper, it's better to prevent by choosing coins that are in the top 10 at CMC.
Some actually can be known in the beginning they released their project. like web, whitepaper, and other aspects. but some projects do and work very neatly so we can't find mistakes from projects. many were even caught when ICO sales were finished. most important when seeing something that is not fair in a project better do not approach it.