There are several tools available to help you read journal articles. These are called critical appraisal tools and they help you to assess the quality and relevance of journal articles.
Critical Appraisal Skills Programme (CASP) Tools from Solutions for Public Health
University of Oxford Centre for Evidence Based Medicine Directory
Canadian Centre for Health Evidence - Users Guides to the Medical Literature
How to read a paper - Professor Trisha Greenhalgh (Athens account required to read the full text)