In a lot of research you have to site sources from a "reputable" journal. I've seen journals that have opened simply to post that bigfoot exists and won't take anything other than more or less garbage papers. Not to mention the problem with people "fixing" data to make their paper look legitimate when it's not.
How can I tell if the journal (and subsequent articles) I'm looking at is reputable?
If you know your field, it is easy to know how reputable some journal is. You find papers in it by the best people in your field publishing the most important results there you are already familiar with.
On the other hand if you do not know your field yet, I would advise you to get to know it at the glance at least first. Familiarise yourself with the most important and fundamental results and findings and the most influential authors. You should identify these authors quickly by seeing them in many various papers cited again and again by different researchers. Then look where these authors published the papers to find out what journals are likely to be more reliable than others.
Moreover, if you know your field, you should be able to discern a value and validity of a paper quickly from the abstract.
You might find useful to check if the journal you're looking at is not part of Beall's List of Predatory Publishers: http://scholarlyoa.com/2015/01/02/bealls-list-of-predatory-publishers-2015/
