That's a complicated question and something I have had to figure out on my own. Some of my investments and mining strategies have paid off, others have flopped and left me in the hole.
I would recommend looking at the crypto's website and thinking about how it is unique or has potential for use. Keep in mind a lot of coins are designed to just pump and dump making those in-the-know rich. Experiment with small investments and other tests. Don't believe everything you read.
Hope that helps. My website is designed as an educational resource for those new to cryptos if you want to check it out:
http://bitcoinstory.org/Like you said it very complicated question. Maybe you just need to have a hunch for it and buy it when is at low price. Maybe this site will help you decide
http://cryptmarketcap.com/. Here you can find list of 64 coins and alt coins and also market cap, volume, how much coins is mined and coin change up or down in %. It's interesting watching moon coin now... He rice day by day .
Cheers