The first step in evaluating the research is to understand the different types of research studies. The University of Minnesota has a guide provides a good overview of the different study types.
Once you have a good understanding of the different types of studies, the next step is evaluating individual studies by critically appraising the study to determine if it will help with your research question.
The Centre for Evidence-Based Medicine (CEBM) has a great page with sample worksheets to help evaluate individual articles. Their worksheets will help you establish
1. Does the study address a clearly focused question?
2. Did the survey use valid methods to address the question?
3. Are the valid results of this study important?
4. Are these valid, important results applicable to my patient or population?
If the answer to any of the above questions is no, then you do not need to read that article and it should not be used as evidence for your decision making process. The CEBM's worksheets are available in English, Chinese, German, Lithuanian, Portuguese, and Spanish.
For more information I recommend reading
A compendium of Critical Appraisal Tools for Public Health Practice written by Donna Ciliska, Helen Thomas, and M. Katherine Buffett.
They refer to numerous resources for critical appraisal, some linked to here and many more.