In addition to ensuring sources are scholarly, consider...
Currency: When was the information created or published? Do you need more current information?
Content: Is the information accurate? Does it provide in-depth information or just a summary?
Viewpoint: How does publication date, publisher or other factors affect viewpoint? How opinionated is the piece?
Relevance: Is the information important for your needs? Do you need a source to get ideas, or to cite in your paper?