you must look into a lot of aspects but the main ones are
1) team (real or not, investigate)
2) whitepaper
3) product (finished or not)
4) use case for product
5) cap and token sale details
I am sure there are few more but those are most important
i would say use case is overlooked way too much these days,
sure short term profits can be made from trading coins without a future but the real money is made from those with long term potential.