This covers the D70 and SB-600 which I use personally. It should be similar on other cameras. Any questions? Presuming you have USA equipment, call (800) NIKON-UX for details.

On your D70:

Use P, S, A or M exposure mode.

Press MENU. Go to the yellow wrench menu, and be sure CSM MENU is set to DETAILED. Otherwise you won't see the next setting!

Go to the CSM menu which looks like a purple pencil. Set #19, Flash Mode, to "COMMANDER MODE." Further click to the right to set the commander mode to "TTL."

You also may set the commander mode to Manual or AA, which are other modes to fire the remote flash. The SB-600 only works with TTL and Manual. You set the manual power level at the camera.

Don't forget to POP UP THE BUILT-IN FLASH!

On your D200:

Press MENU.

Move up or down to: PENCIL menu.

Move right and down to: e Bracketing/Flash

Move right and down to: e3: Built-in Flash

Move right and down to: C Commander Mode

Move right to get to a confusing panel of C Commander Mode settings.

Once in this confusing panel you can set everything for two external groups of flashes and the built-in flash. You move between the different fields by moving left and right, and set any field by toggling up and down.

In this panel you must select Channel, and set it to 3. Default is 1, which is the default for the SB-800. Don't ask me why they are different. Default for the SB-600 flash is channel 3, so if you forget this it won't work! Sorry about the complexity; Nikon didn't ask me for help here.

This is such a pain I use one of the D200's setting banks to store this.

On your SB-600:

Hold down ZOOM and "-" together to enter the CSM settings. That's why you see a gray "CSM" marking between those two buttons.

Press either the + or - buttons until you see an icon that looks like a wiggly Z-shaped arrow. This arrow refers to wireless communication between the flash and camera. When you see the wiggly arrow, press MODE to make it say ON.

Press ZOOM and "-" together to get out of the CSM mode. Even easier, just tap the power button to get back to normal operation. It won't turn off if you hit it while in the CSM settings.

Presuming you did this correctly you'll see "CHannel 3" and "GROUP A" displayed. If you see different channels or groups then press MODE to get one or the other to flash and then the + or - buttons to set them back to 3 and A. No, I have no idea why these are the settings you have to use instead of 1 and A; 3 and A are what you need to talk to the D70's built in flash. If you get smart and choose others then it won't work. The other channels and groups are for people much smarter than I who want to try to rig up a zillion flashes to work together and control them all separately and remotely. I prefer professional studio strobes if I'm using more than one strobe at a time.

The SB-600 doesn't go into standby in this mode, so you can run down your batteries if you forget and leave it this way. It just sits there blinking its little red LEDs visible from the front.

HOW TO SHOOT

Easy, just shoot! If you set everything to TTL as I suggest then the camera just does everything. You and I are free to concentrate on the more important parts of making a great image.

Everything is controlled from your camera. This is very convenient if you have the strobes someplace remote, like duct taped behind plants.

You can control the remote flash's output simply by varying the flash exposure compensation control on the camera. You can do that without taking your eye away from the finder! You do that by pressing the same button you used to pop up the flash and then moving the front control wheel. You'll see the amount of compensation on both the camera's top LCD as well as through the finder. Brilliant! You can add more or less flash fill without having to walk over to the remote flash.

You can set the mode (TTL, Manual or AA) from the camera.

You can set the manual power level from the camera as well.

Try to have the little black window on the bottom right of the flash (marked with that same wiggly arrow) pointing in the general direction of the camera. Thankfully it's not a big deal; you don't even need a line of sight so long as the flash is anywhere near the camera or subject.

The sensor is sensitive enough to pick up the flash from the camera even if it has to bounce around a corner or off the subject. This makes this current system so much better than the older ones. You can hide flashes anyplace and even if they can't see the camera they usually go off correctly. They beep to let you know what's going on, even if you cant' see them.

The i-TTL system is much better than the old systems because it just works. If you ever used the older systems you'd know that half the time you'd get no flash, or a full-power flash that also wasted the shot. This new system just works, and that's critical for use in the field where the remote flash is rested on a garbage can or held in your left hand while you hold the camera with your right.

I even can have the flash in a different room out of view of the camera and it goes off just fine.

It works fine even 50 feet away. I haven't tried it any further. Honestly I have no need for a flash that far away; I was just seeing if it worked.