If, upon searching, you realize that there is not enough information to form a good argument, you may have to alter your topic or thesis statement. Sometimes this requires minimal changes, such as arguing the other side of a subject, but sometimes it may be better to find a different topic.
There is a difference between scholarly, peer-reviewed articles and those that are posted on the internet. Although well-researched articles can be posted online, most articles published online have not been reviewed to the extent that journals from a database have.
Does the author have credentials or anything that qualifies them as "experts" on the subject? If not, their opinions may not be beneficial in building a well-presented argument.
Consider how long ago the material was written. In some fields, such as the sciences, new discoveries are constantly being made. Make sure that the information you are researching is not outdated, presenting up to date information will help strengthen your argument.
Is the information presented directed toward a specific audience? If so, consider the source's compatibility with your target audience.
Sources can either be "Primary" or "Secondary" Text. For example, sometimes a source provides good information but written poorly or at a lower standard. In this case, you would want to use the source's information as a Secondary Text, reserving Primary Text for the those that represent high-quality material.
When researching it can be hard to find information relevant to a specific topic. Be careful when using search keywords. Be sure not to use too broad of terms, while also making sure that you are not limiting your search with words that are too specific.