How to find the flight paths of an airport?
You can find a great deal of approach path information here but that will only give you the path, and perhaps some intercept altitudes for a given approach it will not give you any speed information. Cruising altitudes will also vary heavily by aircraft type.  


  Specifically, I need a figure showing the height vs. speed of a plane
  as it's landing starting from the cruising altitude.


This is broadly specific to each airframe as well as the loading of any given aircraft at a given time. But you can find the information if you know the airframe in question, there are also some limits depending on where you are in the world. The FAA (and presumably most legal entities) cant have different rules for everyone so they broadly break down approach speeds into categories. That should give you a fair idea of the approach speeds. Keep in mind these are airspeeds and local wind will alter ground speeds on an individual day basis.  

If you start from the cruising altitude there will be a few phases of the decent that will see various speeds. This depends on what ATC clears you for and what the local conditions call for more on that here.