The quickest way is to choose the close-up program from your camera’s vari-programs/scene modes menu. The camera will set a relatively small aperture – about f/5.6 for enough depth-of-field to create a striking close-up photograph.
Lens choice is vital to the capturing a sharp, frame-filling close-up. If you’re using a NIKKOR zoom with close-up capability, zoom out to the telephoto end of the focal length range and compose your image. Be aware of the closest focusing distance of the lens you’re using; if you’re closer to your subject than that limit allows, you won’t be able to get a sharp picture. For the ultimate in close focusing capability, consider a Micro-NIKKOR lens. Available in focal lengths of 60mm, 105mm and 200mm, they are designed specifically for close-up photography.
If you’re using a NIKKOR image stabilization lens (it will have a VR, for vibration reduction, designation), activate the VR to insure the sharpest possible image. If you’ve got a tripod, use it—and be sure VR is turned off.