there are many step in which you can find out the potential of altcoins.
1) go to coinmarketcap check the total supply if total supply is more then the chances of price increase is very slow.
2) if coin is listed on high volume Exchanges like binance bitrex they have higher chance and there 24hour volume is less then 5million then there is huge chance it can increase in 24 hrs.
3) its depend on the team associated with the project how the team work behind on the project. and the partnership with other company
all these factors depend on the potential of the coin