Each person has different kinds of psychological needs. If a job helps a person satisfy those needs, it will make him happy. For example, if you value freedom, a desk job that keeps you locked in an office might not make you happy.
When a person finds a job that matches his passion he usually feels great about it and his chances of success become much higher. Find your passion then try to find a job related to it.
Your hobbies can direct you towards your passion. If you have some hobbies that you like, try to find a job related to them. Our hobbies usually reflect our important psychological needs and this is why we feel good when we do them.
Talk to people who work in the different fields and get some feedback from them. This feedback can help you know more about each job and so increase your chances of finding the right one.
If you studied something that you didn't like, don't work in that field just because all of the people who studied with you in college did the same. People who choose popular jobs or ones that everyone else are after without having passion for them usually feel unhappy.
Some companies provide short term internships for students. Going for an internship can help you see a company from the inside and experience the daily work routine you would experience if you got that job.
Sometimes the only way to find the right job is to try more than one job and find the place you feel comfortable at the most. The more jobs you try, the more likely you are going to find the one that matches your preferences.
The subjects you liked in school might give a good indication of the kind of job that might appeal to you. If you liked science and biology, for example, then finding a related job might be a good idea.
According to Wikipedia, the Occupational Outlook Handbook is a publication of the United States Department of Labor's Bureau of Labor Statistics that includes information about the nature of work, working conditions, training and education, earnings and job outlook of different jobs.
If, for example, you love to travel often then a job that would keep you grounded in one area might not be good for you. It's important to find a job that matches your lifestyle so that it makes you comfortable.
Some jobs have a limited future potential, while others can lead to great career advances. Knowing where you want to be in the future is crucial for selecting a job. By understanding where you want to be in the future, you will be able to take the right first step.
The more you understand yourself, the more likely you are going to select the right job. So many people become dissatisfied with their lives just because they chose jobs that didn't match their personalities or needs.
The key to finding one's passion is finding the job that you don't mind doing for free. This kind of job is usually the job you will be able to succeed at as you will keep going with it no matter how hard things get.
If you are good at computers, for example, then finding a computer related job might be a good idea. Find out your skills and the things you are good at for they can help you choose the right career.