team background & transparency, competitors on the market, token valuation, roadmap, etc. it's extremely difficult to research all tokens on the market on your own. it is okay if you join group and follow the hype but before you buy anything, make some research first. follow the hype, stay for the fundamentals, don't get too attached to a project.
definitely, in this sense I like to be tuned on twitter to keep up with updates
there are lots of good information there if you know how to filter.
also: experience teaches a lot!