you have a programmable function button on the left side just behind the lens mount. i programmed it to do ISO. i tell you this because in manual mode in night shots, make sure you lower your ISO to like 100-200If it's anything like the D50's...
On manual, use the little circular dial thing on the right.
Left = slower shutter speed, right = faster shutter speed
Hold the +/- button on the top and use dial to adjust aperature.