Turn off VR or IS

Lens feature Vibration Reduction (VR by Nikon) and Image Stabilization (IS by Canon) is a very nice feature. And can save you when no tripod on your side.

However, when tripod on your side, turn off this feature, and you'll get sharper images. In non-technical, VR or IS lens, will look for vibrations and when they are not found, this feature will keep searching, even cause a small vibration that cause you get less sharp image.