Okay, here some kind of mini-tutorial... place hint brushes in a way that they are put some 8-16 units into a wall:

Place them like this, always around corners, look at the red outlines, these should be hints:

This is the effect, near to the stairs it renders them:

And strafing away the stairs are not rendered anymore, the are not in the PVS (potential visibility set) because of the hint brushes:

Hint brushes just give the compiler a hint what a player can see from any position. Stuff that is not needed is not rendered with hints.
I hope I could help...

Danny