To me the key is determining which coins will do well....no different from investing $$ directly. i.e.

Good idea. The coin is different and adds value in some way. Not just another ERC20 coin
Whitepaper that looks legit.
Website that looks legit
Team. Discloses team at appropriate time.
Transparent thread. Creators of coin address questions openly and address concerns. They should also seem technically competent.
Roadmap targets being hit.