DeepOnion has just been released on the exchange and is set to do exceptionally well. Trezar is also one to look out for. Neo is a definite and I'd say NXS to but it'll need a while to recover. (Then again, which alt doesn't at the moment!?) As the rest of the guys have said though it's about really understanding the coin your investing in and also analysing the market. There's never 100% certainty though.
I never know how to choose a good coin. I just picked the famous coin and coins that cost a lot. Currently there are some coins that cost the most expensive in the market. Such as:
Bitcoin, Ethereum, Litecoin, Dash, Zcash, Monero, and others.
Usually the coin is discussed and used as an
investment tool. But for a new coin like the one with new ICO, I'm a bit hesitant and do not want to invest first. I just want to invest into a coin that is definitely profit just like
Bitcoin. And for mining, I think
Ethereum is the best. And also, there is a very unique coin called
Dogecoin. Although the price of the coin never changes, but I like to use it for transactions. Because it can be free from the risk of profit and loss.