1) Run 'make config' or 'make menuconfig' and select the 
   functionality that you wish to enable.

2) Run 'make dep'

3) Check the Makefile for any Makefile setting you wish 
    to adjust for your system (things like like setting 
    your cross compiler, adjusting optimizations, etc)

4) Run 'make'

5) Go get a drink of water, drink a soda, visit the bathroom,
    or whatever while it compiles.  It doesn't take very
    long to compile, so you don't really need to waste too
    much time waiting...

6) Run 'make install' or 'make PREFIX=/target install' to
    install busybox and all the needed links.  Some people
    will prefer to install using hardlinks and will instead
    want to run 'make install-hardlinks'....