Have a letter of resignation prepared
The best way to leave a company is to give a letter of resignation to your boss. That means you can’t quit with an instant message or over the phone. We’re talking a letter with the company name and address at the top as well as your name signed at the bottom. Although we’re in the age of electronic correspondence, a proper resignation letter should be formally typed and submitted in person. Outline what you’ve enjoyed about your job and the company and explain why you’re choosing to leave.
Thank your boss for what he/she has taught you. Remember... chances are that they will keep the letter with their portfolio of you and that will make them think twice about recommending you to your new boss.
Dont slack off
Just because you are quitting doesn't mean you need to stop working hard. You should always leave others with a good last impression of you.
What to Say
Don't say much more than you are leaving. Emphasize the positive and talk about how the company has benefited you, but, mention that it's time to move on. Offer to help during the transition and afterwards. Don't be negative. There's no point - you're leaving and you want to leave on good terms.
Take only what is yours
When you finally are ready to leave your post, take only the belongings that are yours and leave company property where it belongs. It can create a conflict of interest or even a bad taste in the mouth of your former employer to find you have absconded with office supplies, computer software, or other company belongings. Some companies will go so far as taking legal action, so only take what is yours rather than risk ruining your reputation.
Who knows where you'll end up after this new job? The world is mobile. Keep your network of trusted friends, colleagues and advisors warm. If you've done good work, built real or meaningful relationships, or even just gained a valuable skillset, don't throw away all of that experience by pretending these years of your life didn't exist.