Joining in bounties are easy but finding a good project is hard. So to make sure you join in a campaign take time researching.
Your advice is good, but not everyone will do a mini research, that's why many people make the same mistakes again and again.
The key are doing mini research, analysis, think then take action.
Projects are always made in a way that they look very strong in paper but most of those doesn't look that strong after raising the initial capital and after getting an exchange listing, their condition become poor after watching so many price dumps that happens. Also it is said wisely that never judge a book by it's cover and these social media handles, website and Whitepaper are just a cover for those projects, the reality lies behind the curtain which only a few people are allowed to open.
But even with these so said covers we can actually do a basic search and when we like a project that stands out, then we can join it, just like the bounty of which I am currently a part of, Idena is a really good project with proof of people and I am also buying the coins and gonna hold them for atleast when the experimental mainnet goes main stream.