You should consider a number of factors when deciding which open access journal to publish in, and many of those factors are the same ones you would consider when deciding which paywalled journal to publish in. Watch this video from Think. Check. Submit. on things to consider when choosing a journal.
Other factors to consider:
The journal is listed in the Directory of Open Access Journals.
You can also check to see if a journal has been removed from DOAJ and for what reason or see if it has claimed to be listed in DOAJ when it has not.
The publisher is a member of the Open Access Scholarly Publishers Association and/or the Committee of Publication Ethics.
The journal has a clearly defined scope.
The journal clearly lists all members of its editorial board and its publisher.
The journal is affiliated with a known scholarly society or academic institution.
The journal is also up front and clear about its policy in regards to copyright and what, if any, licensing it uses for articles (such as a Creative Commons license).
The journal has both an ISSN (International Standard Serial Number) and, for each article, a DOI (Digital Object Identifier).
Editors do not send obtrusive marketing emails and narrowly focus emails seeking contributions to those in the appropriate fields.
If the journal claims to be indexed by specific databases, verify it actually is.
If you're still not sure, you can also use COPE's codes of best practices for journal publishers and editors as a guide for evaluating a journal.
Not sure if a conference is worth attending? Check out Think. Check. Attend.
Interested in starting your own open access journal? Check out these guides for tips on starting a small journal.
