I wish I knew...
The best I can say is you can figure it out after the fact. Even legit coins have a pump-and-dump phase, probably because there's so many people looking to jump on anything for a quick buck. Also, the coins are usually rigged so that the coin rewards are biggest early in the mining cycle: that supply tsunami all-but-guarantees a dump. My advice? Wait until the dump phase is over and then check out the coin. You can buy in at a low price when the quick-buck types get frustrated with it and move to the next one.
If you're going to play the game this way, check out the community; that's a vital part of the due diligence. A growing community is no guarantee, of course, but it does give a coin a leg up. Warning: there's a big difference between a
growing community and an
enthusiastic community. Small communities can make big noises.
Oh, yes. If you play the game this way, you'd better have patience 'cos you're in for a long wait. That's actually a blessing in disguise, because it means you can jump into the community itself and help out a little. Or - perish the thought
- take some time and learn the technical nuts-and-bolts of your coin.