there definitely are good coins out there, and there definitely are bad coins as well. You can't predict everything of course and it's difficult to foresee if something goes right or wrong (you basically can't), but what you can do is be sure that you're investing in a good project. In order to ensure that you can check the whitepaper and read it several times trying to figure out whether what is written in it makes sense and if the goals indicated are feasible. Unfortunately many are just following the hype, and whatever coin is being talked about is the one that usually profits a lot. But what you have to do is actually spend a lot of time talking with the community and founders before investors in a coin. It's not easy but if done right you can profit greatly.