Look for these sections (which may not be specifically marked) to determine if the article is a research paper. Also look for key phrases, especially in the abstract, like "this study", "we determined/measured/surveyed/etc.", anything refering to the population studied or the experimental design, etc.
Summary--does this article really cover what you need?
Overview and lit review--skim or read for background
What did they do--check for population (middle school students, seniors over 65 with heart conditions, etc.), otherwise skip or skim
What they found--numbers, responses, etc. NOT interpretation--skip or skim
What the results mean--the most important part of the article in most cases. Read carefully.
Summary of discussion and results. Future implications and research. May simply be the final paragraph of article.
Previous work cited in the article--the foundations of the research. Skim for related papers of interest and for specific articles mentioned in crucial sections of the article.
These are tips for recognizing a research article, as opposed to a review, a summary, a critique, a news article, or other type of article. To fully understand the research done you will need to carefully review the entire article. Skipping or skimming sections is fine for getting the general idea of the research. To evaluate the research, compare the research to other experiments, or to build off the research will require reviewing even the parts labeled 'skip or skim' above.