Know Your Nikon
Have you thought about how you are going to accomplish your self portrait?
What equipment will you be using? Will you need studio lighting to accomplish your vision? Will you need to set your camera up on a timer? Use a tripod?
Do you know, roughly, what settings you will need to use on your camera to make your vision come true?
Start setting up an area where you will be shooting your photograph and test the waters. Is what you are doing helping you get to your final image? If not, how are you going to adjust your settings, in camera and out of camera, to get to your final image?
It's best to think of these things ahead of time, that way when the time comes to shoot your image, you are completely prepared and stress-free.
Photographer, visual artist, and customer service extraordinaire.