I still see some physician offices recommending testicular self-examination for males, adolescent and older. This isn't the right thing to do.
According to the U.S. Preventive Services Task Force, if you have no symptoms, there is no evidence doing self-examination prolongs life or reduces suffering (the two main goals of medicine). In fact, screening can lead to harm through anxiety and complications from unnecessary diagnostic tests and procedures.
Part of the rationale here is that testicular cancer is very rare, so if you find something it's unlikely to be cancer. The other factor is that even if testicular cancer is detected late, it still has a high cure rate.
I'm not making this up: Here's the USPSTF link.
We always feel like if we're doing something, it's better than not doing something. We also feel like if we find a problem earlier, that's better than finding it late. These are common sense approaches.
However, common sense is not be best way to solve all problems. Common sense must be combined with science. For example, brain surgeons don't operate based on common sense alone.
And as in brain surgery, there are many intelligent people who spend their lives trying to determine the best approach to cancer screening. Our common sense is not necessarily smarter than all of them put together.
Note that these recommendations do not apply to males with a history of cryptorchidism, which is undescended testicles. Even if surgery is performed to lower the testicles, cancer risk is still higher than normal.
Also please note that the recommendations do not apply if you have symptoms.