In every field or discipline, there are journals that scholars consider prestigious and influential. Ask your instructors about the most prestigious journals for research in their disciplines.
Journals are judged by a variety of metrics that look at the impact of articles published in that journal. The metrics usually look at how many citations articles published in the journal receive over time. These metrics have received criticism because they are easy to game and are not an accurate measure of quality. See Declaration on Research Assessment and the European Association of Science Editors Statement on Inappropriate use of Impact Factors.
Eigenfactor looks at the impact of journals that are citing each article. Search for a specific journal to view their Eigenfactor, or search by ISI Category to choose a specific field and view the journals ranked by Eigenfactor. If you want to learn more about how Eigenfactor is calculated, take a look at the eigenfactor.org web site.