For steam, the easiest way is shutdown steam, move the folder "C:\Program Files (x86)\Steam\steamapps" to "D:\steamapps\" then open a command shell and use the mklink command
its either
MKLINK /h "C:\Program Files (x86)\Steam\steamapps" d:\steamapps\
or
MKLINK /h d:\steammapps\ "C:\Program Files (x86)\Steam\steamapps"
This makes a hard link between the folder structure of drive c and drive d, all applications looking for this folder on drive c will automagically use drive d instead.
Alternately you could concatenate your drive, but that's much more complex.