Choosing a Clarinet
How to choose a reed

In order to choose the best reeds from a box, first you need to wet them all and give each one a test blow to see how they are. You should choose the ones that let air in easily, so that you don't have to blow too hard.
This is something that is based very much on the feeling of it, so to begin with you should ask someone who can play the clarinet choose the best and the worst ones of the bunch, and then try them out for yourself so you can see the difference.