For choosing a new coin firstly you have to look their community. I think community and project is the most important thing about coins. Surely you can not find any community maybe for bitcoin or ethereum but you can find a community in telegram for too many altcoins. You have to analyze that project. What is their future plans and why that coin will be very valuable in the future etc.
Also you need to look the exchanges. If that coin already listed binance at least you can be sure that is good coin.