I’m going to use three fields as an example: computer science, biology and paleontology. How do keep with interesting developments in each of these fields? Which journals are the most reputable in their respective fields? How do I know that the journal is reputable? If the journal is reputable, how do I know that a particular paper isn’t a fraudulent paper that managed to slip through the cracks?
Read as much as you can, investigate the authors, go to conferences, meet them, ask questions, investigate their funding, try to replicate their results.