Open Access publishing is not without faults. Some publishers that charge authors for submissions may use questionable publishing practices, such as slack or non-existent peer review, or only publishing for the sake of profit.
Note that there is no single criterion that indicates whether or not a publication is reputable. Rather, look for a cumulative effect of more positives or more negatives.
Credit: Largely adapted from Grand Valley State University Open Access Journal Quality Indicators
If you've investigated publishing in an Open Access journal, you may have heard of predatory journals or publishers. These publishers, while certainly not exclusive to OA journals, tend to target authors seeking to publish in OA journals or may contact authors directly asking for manuscripts. They exist exclusively to gain profit. Frequently, these publishers do not initially mention any author fees, but may later ask for a publication fee under the guise of operating as a quality OA journal.
Closely examine the editor, staff, and publisher of the journal: