Like I've got a clue, being a non-professional. However, (for what it's worth) I've thought about how I might have done it if I had a second chance.
From what I've read, breaking into commerical art sounds like something to be attacked on several fronts.
A basic education in the arts if feasible, but not absolutely necessary, the Hildebrants lasted six months in art school and Micheal Whelan a year. Of course they had an education going of their own: the Hildebrants worked as part of the Jam Handy film studio, and Whelan as a medical illustrator.
Deciding on a target market, newspapers, book covers, digital art, whatever.
Practice and exposure and finding someone who works in the area you want and is willing to talk to you.
If profiles of established artists are any guide, it helps to be incredibly talented, but of course, I wouldn't be reading a profile of a given artist if he wasn't. So that does leave open a world of possibilities that just don't make it to the art magazines, such as digital illustration, web design, using the Internet to promote your portfolio, etc.
I'll pass on some of my favorite bits of advice. When asked to define a novelist, a famous one said: "A writer is someone who writes." and of course, the ever popular "Nothing will come of nothing." Maybe the best thing to do is lots of stuff and see what comes up. You can have a heck of a time doing it!
Good Luck. How does your location play into your plans?
"Art is anything you can get away with." -- Marshall McLuhan