The first thing that I would recommend is looking for someone who has a background in music. If you have a friend who has a college degree in music, I would recommend you consider talking to them. Hiring someone that has experience playing the clarinet and a background in classical training is essential, especially with the clarinet. I would also recommend that you talk with a person you're considering working with. Get a better idea of their background, their expertise, and why they're passionate about the clarinet. You could maybe even look to see if any public school teachers offer private lessons. Sometimes, this may be a pricey option, but it's a good investment if you're really serious about playing the clarinet.