Acceptance With Grace. The best_case scenario__and honestly, the most common reaction__is that your boss will accept your resignation with understanding and sincere congratulations. Your manager will be happy to see that you're advancing your career and moving on to something bigger and better.
The Hand_off. Finally, state your willingness to help out with the transition. You don't need to go into great detail (and definitely don't promise anything you can't deliver), but a couple of lines stating that you'll ensure a smooth wrap_up of your duties will show that you're in the game until the very end. Obviously, feel free to adjust this a bit based on your experience and your company culture, then submit it via the typical procedures at your company.