There is an art and science to quitting a job. You can’t just do it without any tact and expect things to go smoothly. You’ve got to make strategic choices based on how important you are to the company. If you’re one of hundreds of employees doing very menial tasks, putting in your two weeks probably won’t make waves. However, if your being in the company is integral to its functioning, be prepared to have a pretty stressful final two weeks of work.
If there’s one thing you should never do after quitting your job, it’s tell your employer where you’re going. Even if you don’t think they would harm you intentionally, there’s always a chance they will retaliate and try to get you to stay in your current position at any cost. One medical worker learned this the hard way when he told his boss about the new practice he planned on working at after quitting.