COPE provides guidelines targeted toward editors, reviewers and authors.
Editors are recommended that they: do not discriminate unfairly and act in an even-handed way; base publication decisions on paper quality and journal fit; protect anonymity of reviewers in any blind review process; develop clear policies that will guard against commercial influence; and develop guidelines for the editorial board and reviewers.
Authors are also expected to follow ethical standards for publishing their work. Work submitted should be original with no instances of plagiarism. All work discussed in the article should be appropriately cited. There should be no copyright or other intellectual property infringement. The manuscript submitted to the journal must not have been published or submitted elsewhere. Any third-party materials, such as images and visuals should have appropriate permissions. Funding that supported the research should be mentioned. Authors should declare any conflicts of interest. Finally, if any error is discovered after submission and author should let the editor know.
Reviewers should commit to providing actionable and timely feedback geared toward improving the quality of publications; report any suspected cases of plagiarism, or recognition of work that has been published elsewhere, to the editor; immediately tell the editor if a submitted article raises any potential conflicts of interest for them; and maintain confidentiality of authors, materials and processes.
If publishers and journals follow these guidelines, you can enter into the paper submission process knowing that it will be fair and ethical.
So, you should submit your paper to a journal and publisher that comply with these ethical standards, but how can you tell which journals do so?