There are many factors to consider when deciding whether a source of information is trustworthy and accurate, or whether a published study is of high quality. Generally, consider the following:
Is this source relevant to your information need? For journal articles, there should be an "abstract" which presents a summary of the article.
What kind of source is this, and what is the purpose of it? Is this a peer reviewed journal article (purpose is usually to share the results of research with other researchers or professionals)? Is it a news article (purpose is to share factual information with the general public)? Is it something else?
Who created this source? Who authored this research study? What is this publication? Who funded this project?
When was this source published? Is it current enough to still be useful for my needs, or might the information be outdated? Is there newer information available?
The resources listed here can help you to conduct a more in-depth appraisal of research publications.