How to find the best journals or articles to read
This depends on your field. In mathematics, physics, and a few related areas there is arXiv.org. From which you get rss feeds or e-mail announcements for individual research areas. This is particularly helpful because there are a huge amount a journals in mathematics and physics and you could never keep up with all of them. 

The added benefit is that most of what you run across on arXiv hasn't made it to a journal yet so it is relatively new and free. Then after you find useful and interesting articles you can keep track of them and find out where they were eventually published. 

Another set of tools that can be useful is a good indexing service that lets you trace backwards and forwards the references from a paper that you know is important. This lets you see not only what the important paper references but also who has referenced it and where they did so. 

Because of the fact that my research field does not yet have a single journal dedicated to my field these are the tools that I use most to find new literature and see what is going on. Of course if you are still looking around for a research field to get into there are the big general topic journals in each area which are a good place to start if you want a big picture.