I'm sure that different athletes (not only with differing sports but also just different persons even within the same sport) have their own ideas.
However, many of them practice on a daily basis and often that interferes with their ability to do much else with life, e. g. hold a job. For something like basketball in the US, those guys are either all (or almost all) professional basketball players so they have their own training regimens and team, e. g. nutritionist, trainer, plus people to take care of the more mundane details of life so that they don't have to (e. g. pick up dry cleaning). Of course playing pro basketball is good training for Olympic basketball so they are set.
Then there's folks at the other end of the spectrum, such as luge. There's no such thing as a professional luge team anywhere in the world (at least, I don't believe there is) so as a result those folks just practice, practice and then practice some more. Since they are a team they need to coordinate such things. And it costs money, to have good equipment, to have a place to practice, and to, perhaps, hold a job with enough flexibility where they can practice regularly. Hence these folks are looking for corporate sponsorships and, in the absense of corporate support, may end up doing personal fundraisers (bake sales, etc.).
Somewhere in the middle are people who might be in college and on a comparable team, such as track. They have decent practice facilities and may or may not have some financial support, but they have other obligations such as making a certain grade point average.
There are also countries where there are training centers just for Olympians. That involves a lot of money, though, and it may not be where a country wants to (or can) spend its resources.
Hence the short answer is -- there are lots of ways of preparing for the Olympics.
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