So you want to fire off some off-camera flash while you are out and about eh? It's not hard, you just need a few things. Here is an example using a Sony 828 camera and a Sunpak 383 flash. You can use anything you want, any camera and flash combo that works. I am currently using a Canon 20D and a Sunpak 555 flash. So the first example is the flash on the camera. You will no doubt recognize this look...
What we will do is get the flash off the camera and on a light stand using a PC cord to trigger the flash. Lets first start with the camera. If your camera does not have a PC port, then use the hotshoe. Just install a PC to hotshoe adapter and connect the PC cord to the adapter.
Next is the flash. Put the lightstand in the position you want it, connect the umbrella adapter to the light stand and then mount the flash to the umbrella adapter. You can also mount an umbrella if you want bounced light.
Now if you want to trigger the flash wirelessly, then you don't need a PC to hotshoe adapter and you don't need the PC cord. You will need a wireless set, in this example a pocketwizard plus transmitter on the camera and a receiver on the flash is being used. (Note: the umbrella is mislabeled, it is actually a 32")