How can pilots differentiate runways and taxiways during landing?
During daytime and good visibility, it should be pretty obvious that runway markings are white and taxiway markings are yellow. Runways have the runway designator in big white numbers at the end and a dashed centerline, while taxiways have a narrow continuous yellow centerline.

During nighttime, you will notice that runway lights are white or yellowish while taxiway lights are green (center) end blue (edge). Additionally, many runways have approach lighting, which taxiways obviously do not.


During low visibility, you won't be trying to identify the runway visually, since you will be performing an instrument approach, which will usually take you all the way to the threshold. For non-precision approaches, where some visual maneuvering is required, the information above regarding markings and lights apply equally.
In addition, taxiways are generally narrower than runways. While many runways do have parallel taxiways that run for the full length of the runway, in many cases the taxiways will have a few bends or be at a slight angle, whereas the runway will be completely straight and wider.
You should always study aerodrome charts and familiarize yourself with the airport layout before attempting to land at an airport. When doing so, pay attention to the airport layout, and try to notice any areas where confusion is likely (such as long straight taxiways that run parallel to a runway). If you come prepared, and pay attention to the details mentioned above, you should be home safe.