Recently there has been an upsurge in the number of predatory journals and publishers. These predators publish anything at all fee. Beall's list is a good starting point but what do scientists need to do to fight these predators?
Those predatory journals are working because of the ignorance of researchers about publishing. Thus, to bring these journals down, researchers have to acquire the right knowledge about the purpose of doing research (not just for promotion), the importance of publishing in peer-reviewed journals, and how to avoid predatory journals.
When we achieve this, no one will publish in these journals and they'll go down.
Many articles end up in such journals because scientists need to publish, and they get rejected by other journals. I think, several things would be helpful:
(1) People need to be much more aware that bad studies ruin their reputation, damage the urgently needed general support for science and may even reinforce prejudice.
(2) Provide fair reviews that to not dismiss flawed studies per se or are aggressively written. I prefer to point out errors and advise how to fix them (also for future manuscripts). I am personally grateful for constructive criticism, because I regard reviewing as a way to improve manuscripts, not to filter them them out. This gatekeeper thinking is a big problem.
(3) We have to communicate scientific standards clearly and explain why these are important. I have seen terrible studies that are basically useless, because these standards were not met at all. I don't believe that these studies are published that way because the authors don't care, maybe they are just not aware of the problem. The communication of these issues should be clear and non-dismissive. I sometimes feel that criticism of an issue is received as a personal insult or even patronizing, although not meant that way. People, criticiser and criticized, have to be aware of that. The combination of pride (personal and national) and strong competition cannot work in a system that aims for truth and progress.
(4) Publish less! Stop splitting data just to make another publication out of the remains. There are WAY TOO MUCH papers popped out every day, most of them not worth the read. One good, valuable publication should be enough for a phd candidate for example, instead of three meaningless papers.
Apart from that: recognizing a predatory journal is not really difficult, see the comments above.
Unfortunately, in several countries, your lab funding or your salary depends on the number of papers you publish (e.g., China, Czech republic). The incentives to publish (and also where) are quite completely out of control. As soon as you have a collaborator, who is affected, you have to think about these issues.