You should look for the most current information in your field because new research is sometimes produced quickly, leaving earlier research in need of updating. Information changes in different time frames in different scientific fields. For example, philosophic information is updated less frequently than that in e.g. technical sciences.
It is important that you recognise the difference between popular and scientific information.
The quality of articles in scientific publications is guaranteed by peer review that is part of the publication process. The scripts of peer reviewed articles are reviewed by experts in the field, and they also decide on their publication. A peer review group consists of experts who review the content of a publication objectively.
You should always use primary sources when working on a research project or thesis. Secondary resources cite and summarise the information taken from a primary source.
When using Internet search engines (e.g. Google) instead of databases established in your field, you should be especially critical towards the information you find. As Internet content is not monitored by any authorised party who can guarantee the validity, accuracy or quality of the information, it is your responsibility as an information-seeker to evaluate the information critically.