It can be tough to choose a clarinet for yourself, your beginning child, or your advancing high school clarinetist. Here are some tips that I have acquired in my experience as a clarinetist and educator.
Where to start:
Start beginners with an intermediate clarinet, if your budget will allow, and then switch to a professional model in high school. If you must purchase a plastic beginner clarinet, choose one of the models below for reliability and durability, then switch to a professional model in high school.
Choose instruments made in the USA or France. These instruments are made from durable, quality material that sounds great and can withstand beginner wear and tear. Cheap instruments will break easily, and are inconsistently made, making replacement parts difficult to impossible for repair technicians to find. Many repair techs will refuse to repair cheaply made instruments. The instruments below are reliable student model clarinets:
(note: I would recommend purchasing a professional model over an intermediate model if you can afford it.)
Clarinet - Intermediate and Professional Model Buying Guide
First, if you have a private instructor, please ask them to help you pick out a new clarinet. Second, always try as many instruments side-by-side as you can. Since quality clarinets are made of wood (a natural material), every instrument is going to feel/sound slightly different.
You will need: New reeds, a tuner, paper, contrasting pieces of music (fast, slow, legato, fast articulation, etc).