When practicing, rehearsing, or performing concentrate as if you are in love, then concentrate even harder.
Many musical skills take weeks or years to bring to a high level.
Place thumb rest in crook of first joint at the base of your nail, curve your fingers gently as if you are picking up a bread crumb. Make sure that none of your fingers rest against a key, or part of the clarinet, when they should not. Place most of the soft part of your bottom lip over bottom teeth. Experiment for the best sound and feel. Place top teeth on mouthpiece.