What to do
After a Computer Science graduation, a world of opportunities is at hand. Of course, CS trains mainly developers, but students could also use knowledge acquired as an advantage to work on other types of activities. One could continue studies and write a thesis. Some may have realized along the way that they were mistaken and that rather than quit in the middle of studies, the should finish their degree and then move on to their real aspirations. These aspirations may be as diverse as sales, management, human relations among others. It might also be that these students became aware of these jobs during their studies and decided for a career change before starting their career.
And then there's the entrepreneur type, one who's interested in all those jobs and/or has an idea for a revolutionary product.
I may have missed a few careers along the way as I am simplifying a lot.
When to choose a career
Usually, people choose a career path during their studies. This depends very much upon the maturity of their personal project. Full maturation takes time and may need trial and error.
This is why choosing a career path should be a constant preoccupation. Not to say that one should always think about it, but at least keep it in mind.
Why should I change career?
Motivations for a career change should not be taken lightly. If you are lucky enough to be able to choose your job, do not mess up this opportunity and choose something that you are even more interested in.
Just to say that money can't be the only motivation.
I've seen poor developers change orientation. Let's say that in that case, it's better to change directions rather that suffer from an uncomfortable situation.
In any case, if you don't love your job, the best thing you can do for yourself is to find the right job.