Although it doesn’t necessarily signal a problem, squeaky stairs can be very annoying. It’s easy enough to ignore, but wouldn’t you rather fix it for good? Luckily, the fix is fairly simple for any home DIY’er.
For basement and lower level stairs, you can usually access the bottom of the structure for a good view of the unfinished side. Shut off the lights underneath the stairs while keeping them on for the other side of the stairs. Look for spots where the light shines through.
If this is not possible, have a partner step on each stair while you listen for noises. You may even be able to see the tread compress on to the riser. Mark each problematic step with a bit of duct tape.