Us e Auto ISO
The Auto ISO setting is very smart: it lets you set the maximum ISO and minimum shutter speed; the camera will increase the ISO only by as much as it has to in order to get the shutter speed you’ve asked for, and won’t let you go higher than your set maximum ISO.
Embrace the dark side
Long exposure noise reduction can reduce digital noise in long-exposure night shots, but it will double the exposure time, as it shoots a second ‘dark frame’ after the actual exposure is taken, to measure noise and then subtract it from the picture.
Keep the noise down
High-ISO noise reduction can make your high-ISO images look less noisy, but it can also smooth out details and textures. On more basic Nikons, it is lumped in with the long-exposure noise reduction feature; more advanced models let you set it separately.