While everyone here has made some important suggestions, I think some explanation is needed.
1.) What do they say in Real Estate? Location Location Location. What do we say in Photography? Composition Composition Composition. Don't just walk around taking point and shoot images. Frame every shot in your mind...how you would like to see it on paper, and then get to that spot before you start tripping the shutter.
2.) ISO - what the other poster said about ISO is accurate. ISO is digital's answer to ASA (also known as film speed). In a nutshell, ISO determines how quickly light will exposure the sensor or "film". The greater the number, the faster it will expose. The downside, especially with Nikon, is the rgeater the #, the poorer the quality of the image. In MOST situations, ISO 400 is suitable for indoors...however, in places where one can not flash, ISO 800 is probably a more acceptable choice. Make sure to tell the camera to turn ISO AUTO OFF. Anything more than ISO 800 on a Nikon body will almost ertainly produce noise. Make surew also to turn your ISO back to 200 when you go outside again during the day.
3.) Tripod - Bring a mini tripod because I guarantee that in most of the settings where you have low light, even at ISO 800 you will not be able to get a good shot because of the length of time the shutter needs to be open. Bring one of those mini pocket sizxed type tripods, and use it whenever and wherever you can. To further eliminate movement, set the shutter on a timer (you camera can do this). Make it wait a few seconds before it trips the shutter. This will allow the camera to be motionless (assuming you set it up on a stable foundation).
4.) Shutter Speed - If you are going to do hand held exposures, set your camera on MANUAL. You can work withe shiutter speed yourself, never going to a speed longer than 1/30. Anything longer than that and you will definitely get blur. It goes without saying that 1/20, and 1/15, and 1/10, etc., are longer exposres...1/40, 1/60 are shorter. Go as short as you can but still maintain a good level of light.
6.) Aperture - when in MANUAL mode, you can adjust shutter speed (like we discussed above) and aperture. While the other poster stated that f8 to f11 is deired (that is very true), it may not be possible. You may have to take your lens to it's maximum aperture (the smaller the #, the greater the aperture). Most good lenses will stop down to f2.8. Most "kit" lenses will stop down to either f3.5 or f4. Whatever it is, don;t be afraid to go there. Go down as far as you have to to get adequate light.
7.) Focus - especially important when you stop down to your maximum aperture. If you have your camera maxed out at f2.8, and a shutter of 1/30 or slower (remember the tripod for anything slower than 1/30) and ISO 800, set the focus on INFINITE. Turn your auto focus off, and dial in the infinite symbol (looks like a sideways figure 8. Make sure to check it before every exposure...especially if you mave moved your camera.
6.) Take more than one - Always take more than one frame. I suaully take 3 and choose the best of them. I also "bracket" these kinds of shots...do a google search on bracketing if you feel up to that challenge.
Follow those tips and even an amateur can get good results. I also teach photography classes...feel free to inquire.