When the time comes to quit a job, your current employer needs sufficient notice to find your replacement. Thus, try to give your employer at least a two-week notice or more, if possible. If you are unable to do that, at least act as quickly as you can. Do it in writing and be sure it contains several components.
Do not simply quit and walk out. Professional courtesy dictates that you provide notice; plus, if you ever feel the need to rejoin that employer, it will never happen after you left on those terms. Also, if a prospective new employer calls this one for a reference, you may have doomed your chances. At best, your old employer will not give a bad reference but will not say anything good either. Then there is the possibility you may one day work with a fellow employee who feels you left everyone in the lurch. You do not want that reputation to follow you. Thus, tell your current employer verbally and in writing why and when you are leaving. Keep all communication as professional and positive as possible.
Put your name, address, and current phone number each on its own line.
Leave a space, then insert the date when you are going to submit the notice.
Leave another space and then address the letter to your boss or to human resources.
State clearly why you are leaving in the body of your letter. Keep your reason as positive as you can. For example, do not say, "I hate my boss so I found a new job." A more artful, diplomatic reason is, "I found a new job that I feel better suits my needs."
Proofread carefully and make all necessary corrections. Make an extra copy of the letter for your records.
Send another notice to quit via certified mail if you have major problems with your current employer. This provides concrete evidence that you indeed gave the company notice. Such documentation could perhaps become important in securing future positions or unemployment benefits.
Say nothing rude or unprofessional if your employer tries dissuading you from quitting. Take time to think about your true goals and needs.
Remember, jobs are hard to find in today's job market; thus, make no hasty moves you may later regret. Don't burn any bridges on your way to the top. Those same people may later prove helpful if you fall.