1. The brand: probably Nikon or Canon

2. The model: you may want to do a lot of shooting in continuous mode as many photojournalists do. If so, you should do some research on which camera bodies support the most frames per second.

3. The lens collection you plan to carry with you. Both Nikon and Canon have similar lenses but you may or may not like particular lenses in each line.

Many photojournalists who use Canon cameras use two lenses mainly:

Canon EF 24-70mm f/2.8L USM
Canon EF 70-200 f/2.8L IS USM

With those two lenses you can capture quite a bit. Not great for paparazzi shooting, for that you need a longer lens, but for most things these two will work very well.

They are both heavy, expensive, and very durable (will last a long time and take abuse).

They both work on any Canon DSLR body: the 400D, the 30D, the 5D and the various 1D models.

The 5D and 1D models are full-frame cameras which means that the sensors on them are a full 35mm which means that the focal lengths of these lenses will be the same as on a film camera. The 400D and 30D and all Nikon bodies are smaller sensors (cropped) and because of this the lens focal lengths need to be multiplied by 1.6 to get the more accurate field of view. The 24 is more like a 40mm and the 200 end of the long zoom is more like a 300mm lens.

Many photojournalists have two cameras, one with one of these lenses, the other with the other mounted so no lens changing on the fly. Having a backup body during an important shoot isn’t a bad idea.

You also should probably have a flash and for the longer zoom you might consider a mono-pod as it’s heavy.

Let me know if that helps. I’m not a photojournalist myself so I’m just telling you what I’ve learned from watching others.

I have a Canon 5D and many lenses, including the above mentioned 24-70mm which I like very much.