How to keep up with the latest peer-reviewed research in a particular field?

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?