First, you need to determine if you need a primary or secondary source or you may need both. Primary sources are first-hand accounts of a topic or event, from people who had a direct connection with it. They represent original thinking and reporting. Diaries, first hand newspaper articles, auto-biographies are examples of primary sources. However, they are not limited to written sources. A primary source can also include music, photos, paintings, etc. Click on this link to learn more about primary sources: primary sources. Secondary sources are written about a topic or after an event and involve analysis, synthesis, interpretation, or an evaluation of a primary source. Examples of secondary sources include biographies, textbooks, books about a primary source...etc. For more information on secondary sources, click on this link: secondary sources.
Once you have determined they type of source you need, you can evaluate if it is a good source by following this guide:
This depends on the type of paper. A historical paper on a historical event or an English paper about a novel can use older sources and primary sources. A paper on medical research usually needs the most up-to-date research and sources.
How is the author(s)? Are they credible? What is their background (education, career...)? Has the information been peer reviewed? Is the information presented cited? Look for footnotes, bibliographies, citations...
Who is the intended audience for the source? For example, if you are using a website as a source, is the website for entertainment or for education? A magazine article's audience (usually for entertainment and light education) would be different than a peer reviewed journal's audience (usually for research and education.)
Check for relevance to your topic. You can check a book summary or an article abstract to get a brief summation of the source to check for its relevance and usefulness for your topic and research.
Every source is presenting a perspective. Opposite perspectives can be helpful in presenting your argument or thesis, but beware of sources that present an extreme bias as they can often misrepresent information. This link, Recognizing Bias, helps understand and to recognize bias in writing.