To know that you'll have to read a lot. Some of the coins that I personally think have a huge potential are Vechain and ethereum. They both gave me good returns in the past.
I can say with absolute surity that Vechain has a lot of potential. It is not due to the returns that it gave me but the concept is quite nice.(offering blockchain as a service). Do give a read about it.
Peace.
This is the only way, each one of us is going to have a few coins in mind but while it is a good idea to ask other people what they think at the end you will need to double check that information and see for yourself if the recommendations you were given are worthy of your investment, you will probably need to dedicate a few hours each day for several days or even weeks just to find a good project.