Hi,
there are several ways to get published:
Contacting magazines by yourself:
First of all, you need to have a book. And depending on the magazine you aim,
you need to build your book in consequence.
A fashion magazine won't be interested in your insect macrophotography, that's evident
So try to contact them, tell you have pictures that might interest them and have an appointment/interview with them.
If they're interested, you maybe could sell them some pictures.
Publish on the Internet and get a lot of attention
This is not the most easiest way, but with very low chance rate since there is a lot of rubbish on sites like Flick-r
(my first photos were very bad too! I should remove them from Flick-r
).
And a lot of people say Waa and Hooo and Wooow, nice bokeh etc... even if the picture is not interesting at all.
Very hard to get noticed (and then published) IMHO.
Participate in national/international/famous/etc. contests
This is another good way for getting published, at least, if you are among the best.
If so, media will get interested in you and you may get proposals (right word?) for getting
published in a photo-dedicated magazine.
I think this is the most glorious way for getting published.
Become a journalist/reporter
And make a lot of good pictures. If people appreciate them, more and more,
you'll become a recognized reporter and people will know you exist.
This is not very easy though. Mayeb start with local press.
Get a contract with some brand
This applies allmost 100% to studio photography. But this is a way to have a 4x12 meter
poster of your photo and model (human or not) on the side of the road.
I don't have much knowledge about this, how to get in the business, but it is a solution.
Maybe there are other ways, but these are the most evident for me..
I'm sure other people will have some other ideas.
Anyway, I wish you good luck!