It depends on what is on the floor that is squeaking. I'm no expert, but I have seen screws that you screw right through carpet into the joist and then it breaks off so you don't see the screw from above at all. Hopefully not from below either.

Tell us what kind of floor you have so others can comment on that. I have tile so the above mentioned suggestion will not work for me. I'm scared to screw in from below for fear I will get into the tile.

Good luck,
Devildog

One problem we found in having a new home built is some 'play' between the joists and support beams. Try tapping in some wood shims in the area where it is squeaking and see if that helps. Also can add shims between flooring and joists CAREFULLY so as not to raise the flooring.

I have no idea what kind of floor it is because it is carpeted. However I will make sure to ask when we do our "walk-through" with the condo people.
Thanks for your responses.