Some factors to consider when critically assessing information:
Currency: When was the resource published or produced? How up to date is it?
Relevance: Who is the intended audience for the resource? Is it relevant to your research topic?
Accuracy: How accurate is the resource? Are there any obvious mistakes?
Authority: How credible is the resource? Has it been peer-reviewed, or come from a reliable source?
Purpose: Why was the resource produced? Is it trying to convince you of a particular agenda or perspective?
The answers to these questions will help you make informed judgments about how to use information. For example, you might include one information source to address a limitation of another.
Whatever your project, these steps should help you find useful material:
Ultimately, searching is not a linear process. The more you read, the more keywords, authors, topics, and questions you will encounter. This reflects your growing knowledge of the topic, and will help you adapt your search terms.
Remember to keep a note of your searching, so that you can repeat it if necessary, and also get due credit for it.