high F# is the three palm keys on the left hand, the octave key, and the top palm key on your right hand.Its' going to sound weird, but you kinda have to put a little more air behind it and tighten...
In order to play a high G on an ALTO saxophone, you play a g and then add the octave key. If you do not know how to play a G, check a fingering chart, and hopefully you know what an octave key is....