At a basic level, check to see if the surgeon is actually a surgeon. Do they have surgical qualifications? In the UK, the minimum is the FRCS (Fellow of the Royal College of Surgeons). This is a rigorous exam to ensure that surgeons learn their anatomy and skills to be safe.
Check and ask questions. If the "surgeon" refers to themselves as "Mr" or "Ms", this is a good start. But still check. The "Dr" suffix is for all non-surgically qualified doctors.
Surgeons become "Mr" after passing the exams for the FRCS.