How to make a floor plan?
There are numerous approaches from simple graph paper (which can be printed out from free online sites, such as this one) to sophisticated paid-for programs, for example one from HGTV.  There are also hard copy layout sets with standard furniture that can be purchased.

You might want to look at one of the free programs, such as Google Sketchup (there is also a more complex paid version). There is a bit of a learning curve, but it has great tools to do three dimensional modeling. The paid version has a two dimensional module called Layout.