Breaking into photojournalism/editorial photogpraphy is very much a "what you can produce" and "who you know" market.
1) What you can produce: I can't tell you how many portfolio's I've reviewed from photographers wanting to "break into photojournalism" that are chock full dull landscapes and and or abstract "fine art photos". Unfortunately, these folks never get a call back. Newspaper/magazine photo editors want to see images of people! People in a variety of situations that convey something (no matter how small) about the person or situation surrounding them. This doesn't have to be war victims and car accidents (please, no more photos of car wrecks! No one wants to see them anymore). I have seen portfolios that contain nothing but images of someone's friends and family that absolutely blew me away! Being able to show versatility and convey emotion is crucial. If you are considering submitting images on spec, be very careful. This is a good way to get taken advantage of.
And getting published for "photo credit" is great once or twice but it's very easy to gain a rep as "the guy (or girl) willing to give their stuff away for nothing.
2) Who you know: Getting your stuff out there is only one part of it. Getting to know people in the business is essential because these are the folks that can get your stuff in front of the RIGHT people. Look at the work of photographers in your area that are doing the kind of stuff you are interested in. See if it would be possible for you to "shadow" them for a day or hell, ask them out to coffee. You'd be surprised how many working photographers are willing to share some of their experience. Chances are, someone gave them a break when they first started.
Also, consider joining the National Press Photographers Association (NPPA). It's not very expensive ($90.00 a year and that includes a subscription to News Photographer Magazine, the organizations highly respected monthly publication) The NPPA is the oldest association for photojournalists in the US and you don't have to "qualify" to join. You just need to have an interest in the profession. You can find a lot of information from organizations like the NPPA, ASMP, and EP (Editorial Photographers). Their websites contain a wealth of info about the business, journalistic ethics, etc.
For reference, those websites are: www.nppa.org, www.asmp.org, and www.editorialphoto.com. In fact, EP has a great little page on "starting out" with advice from top shooters in the biz. Here's the link: http://www.editorialphoto.com/resources/startingout.asp