The most typical way to get started is to use personal connections you have: someone's cousin's brother-in-law is VP at some company, they put in a good word for you, that kind of thing. Or, leverage some connection you have to the previous companies you've worked in, or to former coworkers who've left to go somewhere else, and are in a position to hire contractors. You can also respond to job listings looking for co…
I agree, specialize at all costs. Reading “Book Yourself Solid” and doing the exercises was incredibly helpful to me.
Good luck! There’s a learning curve to sales and marketing just like engineering but we all believe in you! :D