One of the most difficult things is deciding where to publish. Examination of journal rankings and the metrics behind them helps to define which journals are considered highly revered in a particular field (often most-cited). Google Scholar maintains a journal ranking page, but there are certainly better methods for measuring impact.
If you are a scholar planning to publish a journal article, you will no doubt be looking for a reputable journal to provide the best exposure for your work. Be mindful: Making comparisons across different subject areas is difficult; rates of citation are not necessarily stable over time; journal rankings can be affected by self-citations and copious review articles.