For me, I always look on the purpose of the project, the team behind it, what exchanges is it available on etc. And one of the important thing for me is the total supply of the coin.
I also research if the coin is Proof of Work (POW), Proof of Stake (POS), Pre-mined or other.
usually doing a research help a lot specially you will read about the project info like their whitepaper, It is also good if you look unto the team background and successful projects . It will not took a day for you to read those essential thing if you want to have a good coin to invest .