Quantitative measures like Journal Impact Factor are not always available for many disciplines, especially in the humanities. Then you might need qualitiative criteria such as the ones described on this page.
Most academic journals are peer-reviewed, which means papers submitted for consideration are read by at least two scholars knowledgeable about the paper's topic, usually anonymously. A reviewer may accept the paper as is, accept it with recommendations for changes, or reject it. Most databases include peer-review as a filter; you can also look at a journal's "about" pages on its website. If you're still not sure, search the journal name in Ulrichsweb. Peer-reviewed journals are clearly marked with a referee icon.
Investigate a journal's editors and editorial board members. Journals usually list their names, academic degrees, and institutional affiliations, giving enough information to find their pages on institutional websites where their academic training and publications may be listed.
Every academic discipline has at least one or two indexes or databases that are essential tools for doing research in the subject. Most index publishers use some form of a selection process to determine which journals will be indexed to make sure researchers will find the most important articles. You can usually find a list of publications within any given database; or you can search for that publication title.
A journal with low manuscript acceptance rates means a lot of scholars vie to have their articles published there. Some disciplines offer directories of journals that include this information. For example, the Modern Language Association provides a directory of journals indexed in the MLA International Bibliography. Directory information includes acceptance/rejection rates.