If you have a hobby that can be applied into a major (if you like programming, cs) I'd say that should be the first thing you look at. As a cs major myself, most people I know who enjoyed programming beforehand (even if they didn't do too much) tended to do well in the courses (though some people who never did before also picked it up and liked it, but they were not most).
If you have anything you want to learn on your own, a university course is probably the best way to motivate yourself to do it. That would be another thing to consider, if you're interesting it in, you will not only likely enjoy it but also have an easier time with it than many other people.
In the case of careers, your degree opens doors to some but connections do too, and your degree does not tie you to anything. A surprising amount of people in my courses now are people who've worked in cs-related jobs before, but want to get formal schooling for it (either pushed for by their employer, or because they would be more employable in what they already do). Though connections are arguably harder to build and if you have two choices in major with one having plainly better job prospects, I would consider that one all other things equal.
I've known people who entered university/college with a vague idea what they wanted and ended up loving what they did, but I've known just as many who switched majors after a year because they just didn't like / couldn't do what they first majored in. That said, realize that most other people also have no clue what they're supposed to do, and as much as it can seem like an expectation, don't let it pressure you too much. One thing you'll learn pretty soon is that most people who seem like they've got their shit together are mostly just winging it too.