Read their whitepaper!
Yeah. That simple. You look at how unique their project is and how the community would benefit from it. Then next is the team behind it which is really important if they're legit or not. And you can add a little bit of extra research about it.
Of course it won't be recognized at first because a lot of coins listed on the market. But, it can be discoverable if devs keep their coins grow and it's market trend also are moving, then we could say this coins have potentials for good and profitable investment.