If you believe your hard drive is failing: Turn it off. Do not continue to start/boot it up or continue to power it on.
Avoid subjecting the hard drive to static electricity. Hard drives are extremely sensitive and can be damaged severely making data retrieval impossible.
Click on the link in this sentence for telltale signs of hard drive issues.
Never ignore a noisy hard drive or disc boot errors.
Do not, tap, hit or drop your hard drive.
Your actions immediately after
data loss are important as well: if you do anything possible to prevent the storage from further
writing, the chances to get critical files back increase.