Research the team behind the project and the product to be delivered. I also look at something that I can invest into before it releases and has a low market cap. I sugest you look into Ardor before it gets started soon. Also look into Deeponion with the huge potential it has in 2018.
The team behind a project is the most important one, mobilizing the project on a good direction is essential, in the end the team delivers the product, I usually invest in tokens or coins with low circulation supply, low market cap is good but the marketcap is not that important if the coin has huge potential, once it breaks trough and people find out money will flow in and lift your percentages up, I was a huge fan of vertcoin or VTC since the beginning and I still think this coin is going to make it, it will beat Litecoin soon and it is only a matter of time for VTC to have a higher market cap than Litecoin.
Let mr give you a high potential coin: aventus and matchpool. 