Avoiding unethical publishers
The best way to avoid unethical publishers is to have expectations of good service and products.
The Library Guide on Journal Evaluation Tools, which provides a lot of information on journal rankings/metrics, can help you check publisher claims (such as Impact Factors).
Think. Check. Submit. Checklist
This organization has a useful checklist that can be used to see if a journal meets basic publishing expectations. The video, linked below, walks you through the process.