How to execute professional-looking photographs in a dark setting?

I have a Nikon D5100 and I'm very comfortable taking photos in brighter settings or in a morning/afternoon setting. Though when it comes to late afternoon/nighttime settings, I can never execute a great photo. They always turn blurry or the lighting is horrible. How do I take a professional photograph in a dark setting? I usually see photographs of a dark setting with a window shining light and that's sort of what I want to go for.

Shooting "professional-looking photographs" requires you use the same skills a pro uses.

Blur is caused by using too low a shutter speed, so the camera moves during the exposure.

You have to raise the ISO to over 3200 and make sure that the shutter speed 1/250th second or faster.

Blur is either due to out of focus or movement.
The auto focus could be struggling due to the low light but the blur is probably due to you using a slow shutter speed to compensate for the darkness.
There are other ways.
1. Increase the ISO. I leave mine at 1600. The higher you go, the more digital noise.
2. Open the aperture. This is determined by your lens F number. An F2.8 or faster is best for low light, prime lenses are ideal (50mm F1.8, 1.4, 1.2)
3. Slow the shutter speed. If you are still needing to slow the shutter to get enough light, check if your lens has image stabilising. Depending on your lens it could be called IS, OS, VR, or a number of things.
This helps steady the lens for dark shots.
Do some research into the exposure triangle to find out what your best comprimise of the above three will be, and be prepared to buy a faster lens.

To take images in low light without a flash - YOU NEED A TRIPOD.

What you are getting is camera shake blur- caused by using too slow a shutter speed. If you have your camera mounted on a tripod, it will eliminate camera shake.