I believe you have to look at the development team. I'm not interested in too many personal details, what I'm more interested in is their capabilities, what they have produced and what they plan to produce. An example of this is ELTCOIN, most of the developers are not very public as of yet. ELTCOIN does have solid products (iOS and Android wallet). The company which developed ELTCOIN have developed two other companies which will make use of ELTCOIN. All of their software is open-sourced on Github, which is a massive bonus.

Join a coins Telegram and talk to the developers, question them on what you want to know, test their knowledge on crypto and what they've said they're going to do.

If you're going to invest a lot into a coin you need to do your research, find out everything you want to know. Don't just invest in a coin because you see the price rising or because someone else told you to.