Platforms like Preply and italki allow anyone to list as a teacher regardless of qualification. FindEnglishTeacher.com requires every teacher to submit a verifiable teaching qualification before going live.
A verified teaching qualification
CELTA and DELTA require externally assessed practical teaching. Any teacher who cannot produce a verifiable certificate should be treated with caution.
Experience in your specific subject
A general English teacher is not automatically an IELTS or SELT specialist. Ask specifically.
A free trial or level check
Most qualified teachers offer a short introductory session. This is a good sign.