How do you play a high g sharp on a b flat clarinet?

The other two answerers gave you a great chart to use. Experiment with the altissimo range s listed on the link - altissimo s are basically "fake" s because every clarinet will have a different response to them, so you have to figure out which one works best for your horn. Make sure you test these s out with a tuner - intonation can be killer in the altissimo range.