[icey]

Largely dependent on what you mean by "business man", but going from dev to sales can be as easy as transitioning to a sales engineering / solutions architect role and getting exposure to closing deals that way. The next leap you'd make is figuring out how to get into a closing role; which will take a little patience in order to find a good fit (namely: a company willing to put someone with engineering experience in a closing role -- they're out there!).

If you mean other parts of the business (operations, finance, BD, etc), the pattern is probably similar -- find a technical role that's in that org and start there, with the intention of moving into the business side more and more.

If you mean "I'm a software developer and want to understand the business side of running a company better", there is a ton of reading you can do to learn how businesses work. Some books that were helpful to me:

  * The 4 Steps to Epiphany by Steve Blank
  * How to Win Friends and Influence People by Dale Carnegie 
  * The Personal MBA by Josh Kaufman
  * The E-Myth Revisited by Michael Gerber
  * Venture Deals by Brad Feld

Ultimately business skills are gained the same way you'd learn software skills -- self-study combined with exposure to the problems you're interested in solving.