With research and through word of mouth...we must look for coins that are not ico or bounty but people are too stupid for this....I regret I did not get bought coins like litecoin,vertcoin or viacoin when they were very very low in 2015...there is a good dose of luck of course, but you must always do your own researches...for example watch Elicoin in livecoinwatch , is not an ICO or bounty... it's a coin with low mc, low supply, PoW whit cpu, no premine, active dev...only trading it on CREX24 for now...do you own researches in the thread in bitcointalk:
https://bitcointalksearch.org/topic/anneli-elicoin-cpu-mining-only-exchange-available-3028302... people are too stupid for DYOR and got scammed by ICO or bounty...just my 2 cents...hope it helps...cheers
Basically for me, it is always with research, and I get to always familiarize with what is being said on the forum too at times or on review platforms like ICOBench, and then do my own diligence afterwards on the new altcoin and then see if it is something that is going to be worth investing in or not.
Like you said, it is always necessary that no matter where you are getting news of some certain altcoins, or new altcoins, as long as you are a long term investor, you really want to be sure that what you are holding is going to be worth the risk.
There are basically some coins or tokens in the market right now that are not worth the risk, and with some research, I have actually noticed recently that some are even undervalued, for instance COSS.