Hello; This may help if you have some sort of forced air heating or air conditioning with ducts in the floor. The grates in the floor are sometimes not fastened down and can be pull up. I installed carpet for a time and was able to pull the ones set into a floor with my fingers or a gentle application of a screwdriver. Some, like to type in my current home, are nailed to the floor so do not force them.
If you can remove the grates, it may be possible to work out how the joists run. It will depend a lot on how well the ducting was installed. Some times the installer will leave gaps large enough to see thru a bit or the layout can be deciphered by the way they are nailed.
There are stud finders available but the older style that I used were iffy. The newer type may work much better.
If you have a drywall (sheetrock) ceiling it may be possible to see how the panels were screwed to the studs. Some times the installers do not tape and cover the screw dimples all that well and the line of screw dimples can be made out. The edges of sheetrock panels will be screwed to the joists. While it is possible for the cieling joists to run in a different direction than the floor joists, it has not been the case in my experience
The best way is to get under the floor and look, but that may not be possible in an apartment. if you have accesss to the lowest floor of the building, there may be a way to see how the studs run at that level at hope they run the same way in your apartment.