Not all scientific studies are created equal! Study design can impact the strength and quality of evidence that a study holds. This 'Evidence Pyramid' depicts the levels of evidence provided by different types of studies and information. The wide base of the pyramid indicates that there are many editorials and expert opinions, but that they provide the weakest evidence to inform policy and decision-making. There are many fewer systematic reviews on a topic, but these represent the pinnacle of research evidence.
The PICO Framework can be used to structure and refine your research question. This can then be used to structure your search strategy and your process for identifying articles of interest.
When you search for information, you're going to find lots of it . . . but is it good information? You will have to determine that for yourself, and the CRAAP Test can help. The CRAAP Test is a list of questions to help you evaluate the information you find. Different criteria will be more or less important depending on your situation or need. More info here: http://www.csuchico.edu/lins/handouts/eval_websites.pdf