I`ve arranged to purchase a Buffet R13 from a music store, and they tell me they will have 3 or 4 for me too look at and I can have the one I want.

I`d call myself an advanced student, but I do not have a private instructor who can accompany me and tell me whats what and what I should be looking for. Aside from taking what plays the best, I know from experience to check key heights and look for air leaks and pad problems... anything else I should be on the lookout for? Anybody have some advice?

I`d like to leave the store with a perfect instrument

I wouldn`t take a clarinet from the +-list just because it has some air-leaks, they will probably repair it for you on the spot if you tell them to.

If you know anyone who play as good as yourself or better, then you should bring them along (you probably only need one), and you can`t use their favourite clarinet to play on to make you`re decision. You probably don`t have the same taste in how it should sound, so you can only do the decision part by yourself, but you`re friend can tell you how they think it sounds

Make sure that each note plays exactly in tune and at the proper interval from the previous note. Play a full chromatic scale just to do this. Also, make sure the clarinet comes with a proper mouthpiece, as these are acoustically tuned to the instrument.

Actually I wouldn`t care about the mouthpiece. You can always buy a new one. It`s a golden rule to bring your own mouthpiece to pick out a clarinet