To find a promising coin you are to follow all upcoming ICOs and get acquainted with all accessible information. You can look for ICOs and IDOs on coinmarketcap and then investigate web-sites of projects that are about to launch.
You should pay attention to documents, ideas of the project, development team, partnerships and community and I hope you will find the next SOL or ADA one day.
Even after having some good search into ICO's or all things about project we have no guarantee about project because no one know about this it's all depend of developers how they respond after use case and what they want to do but still it's not easy for anyone to have 100% prediction about good project recently we have some good hype in many joke coins which are doing some serious impact on all crypto community.
If you want to live in this crypto community then you have to do some own good search about projects and teams because these things very important for any project success, if developers doing some good then surely it's having good impact on community and project which give them very positive response.