Most agencies usually have stringers in addition to their regular staff photogs so the best way to get your foot (not the whole body!
) into their doors is to start stringing for them. The best approach is to contact the photo editor or chief photog who is the main guy for the photo desk. Try to get a decent portfolio of 15 to 20 photos of various themes and present it to him/her. The portfolio should include sports, fashion shows, press conferences, portraits, features and newsy stuff. Just look through the papers and magazines such as Time, Newsweek, etc to have a better picture (no pun intended) of the kind of pics to go into your portfolio.
Once they decided to try you out for stringing then it will be up to you to prove your worth. However, this will only get you as far as being a regular stringer (assuming you are good) rather than a staff position. Most staff positions are usually, but not always, filled by their own agency photogs as they tend to move from bureau to bureau, eg. a staff photog from Reuters in bureau X requesting or applying for a posting to bureau Y. Make sense? On the rare occasion they might offer a shooting or desk job to their stringer if he/she happens to be in the right place at the right time. Most desk job would usually entail photo editing and the occasional shoot when their shooters are all booked up through other assignments and the writer covering an event needs a photog to accompany him to shoot, edit and file the photos on-site.
I work with 2 AFP staff shooters in Beijing that started with a desk job first and then went on to shoot full time after a couple of years. A good friend of mine got offered a full time position at EPA (in Beijing) after stringing for them for 6 months. So in all honesty, you will need to have a good portfolio, string for the agencies for as long as it takes before you are considered as a viable candidate. Also do check with the agency that you are stringing for if they will let you string for other agencies. Many prefer that you try to stick to one so pick who you want to work with carefully. Reason: conflict of interests. Imagine you string for AP, AFP and Reuters. One day you captured the photo of a lifetime and everyone wants it. Who do you sell it to? The highest bidder? You will find yourself later shun by everyone else other than the highest bidder and that's the best case scenario.
Anyway, good luck! It's a lot of hard work but the fun factor can be pretty high too. However, don't expect to make beaucoup $. Do something else if making $ is your priority. Most of us bitch and moan on rough days but at the end of the day, the worse day shooting still beats the best day in a cubicle of an office building! Unless, of course, you are slaving away at a desk job with one of the big 4 agencies waiting for lady luck to knock on yer door!