Attend only IRCA certified Lead auditor trainings.
Go for Certification bodies / training agencies who are having global presence / well known (For good quality of training).
You can also check feedback of people who has attended the training from the body you are looking to get trained.
If you are arranging this course done in-house, then you can ask to send a trainer who is having good experience (Min 15+ yrs of experience in the field, auditing, etc.).
These are my suggestions, based on how I select a training body for Lead auditor training.
I hope it helps.
Thanks,
Amit