Check reviews that you can trace on facebook for example (to make sure they are real) and speak directly to the trainer to make sure you can get in touch when it comes to ongoing mentoring and case study feedback. Whichever course you choose, expect to work hard (microblading isn't easy), ensure that the course is at least 5 days and forget any course that says they can qualify you without assessment or hands-on coaching. If you can travel to the London area and want the most complete training, check out the Dermagraph microblading course.