Many and various, often no warning signs at all, just sudden death!
Many of the HD manufacturers publish their own little programs to perform basic health checks on an HD.
Have a look for your HD's name and then search the manufacturer's site.
There is a significant list to be found with Google, and dedicated programs to download, but I would caution you about making a hobby of it.
Too rigourus attention could finish an elderly HD
Don't overlook the obvious safety move and back everything up while it is working.
Treat yourself to a copy of Acronis and have a complete installation ready to restore to C: drive on a new HD