1. See if the journal has an impact factor by looking it up by title in Journal Citation Reports.
2. Look at the information about the journal in the Scopus Journal Analyzer. Do the articles published in this journal get cited a lot? How does it stack up against other comparable journals?
3. Look at Scimago and Eigenfactor rankings for the journal.
4. Look at the Google Scholar Journal Rankings. What is the h-5 index of the journal?
5. Look up the journal in Ulrich's to see where it is indexed. If a journal is not indexed by databases that have an editorial policy for journal inclusion, the journal is probably either very new or not very prestigious.
6. Look at the editorial board of the journal. Are the editors of the journal serious scholars and researchers in the field?
7. Look at the articles published in the journal. Do they use rigorous methods and report interesting results? What is your professional opinion of the journal's quality?