If it's just the footsteps a thick carpet will do wonders.
If it's creaking and squeeking you can't do so much with it... Some people get under the stairs and screw a bit of wood in to the tread and riser of the offending step. That's what has happened to my front stairs, now a few years after this I have antique still creaking stairs with the underside covered in bits of 2X4 that shouldn't be there... Old houses creak, and you may just be out of luck with these stairs. Bad repairs like this might help for a few years, but they won't hold.