How to find out what coins are promising?
You need to DYOR. That will be needing your time to be allocated and if there are insightful opinions that you have seen towards a certain coin, take it as a feed back but don't take them quickly as an advise to invest.
You're the one who decides which coin that you're going to invest and not just because it has been said to you to invest, you'll follow them in a heart beat - no.