it depends on the altcoin you are investing ofcourse you have to be very careful there put your own criteria and what suits you Mine is basically
1- the team and how active they are on social media - telegram especially
2- altcoin features what new things the coin is bringing to the table
3- its partnership these days this is actually becoming a universal thing
4- activity on the sites and then social media
Yeah,,, holding ALTS is good if you follow some criteria mentioned above.. but it is very bad that you will regret later to hold scam coins...
So we have to be very selective to what ALTS we are going to invest our money on ~