A locksmith is there to help you during that awful moment when you lock yourself out/in a room/property. People don’t consider the dangers of hiring cowboy locksmiths. There have been many crimes reported where a locksmith breaks into a property at a later date, after observing the layout of the property.
Try and research beforehand. Look at referrals online and have a look through their website. Testimonials on the website don’t necessarily mean they are legitimate, so be wary. Also research the prices charged in your area, if one is charging an extortionately high amount that locksmith may be the one to avoid.