An altcoin, is as good as is the project that creates it. Someone must read the white paper, and try to see if there is a solution, a coin offers. If this is not very clear, better avoid the coin. A good strategy, is to find out an older coin, with similar scope, and check how the market responded. If the market responded well, then you have a use case. If the was no interest from the market, avoid the coin. If there was response, then check that extra, that make this coin different, have a use case for the market, to pay attention. This is not a 100% strategy, but in most cases, you will avoid scam coins.