What ISO, Aperture, and Shutter Speed to use with Flash?

Nikon D3100 with SB700 if it helps. 35mm f/1.8 and 16-85mm f/3.5-f/5.6 lenses are the options.

There's no way to tell in advance, it will depend entirely upon the lighting conditions on the day you shoot and what you are trying to achieve.

You will have to check the exposure yourself. Read the camera user manual that came with your camera - it will tell you how to operate it. The flash will also come with a user manual. Failing that, put it on Auto.

I suggest ISO 200, unless the subject is very far away, in which case raise the ISO. You camera handbook will tell you the fastest shutter speed that can be used with flash, probably 1/160th, but check.

Aperture depends on effect wanted, for small depth of field (background blurred) use a large aperture such as f1.8 or f4, not f11 or f16. If the subject is a long way away you will have to use a large aperture to get enough flash light to hit it.

There's no one setting. When you are just learning - just keep the flash on iTTL, and it will automatically adjust.

However, keep your shutter speed under 1/200 of a second or you will get black bands across the screen. 1/60th is the traditional sync speed for flash use, and it is a good starting point.

It is possible to use a higher shutter speed, up to 1/4000th of a second, but you have to enable your flash and camera Auto FP High Speed Sync (not sure if your camera supports it or not).

When you want to go advanced with your flash, experiment with setting your exposure in the camera to expose the background, and the flash to expose the foreground. That way, you can independently control the foreground and background light levels.

Search YouTube for techniques on doing this by Bryan Peterson.

It all depends on the situation and the lighting effect you are trying to create.

The most common instance for me to use flash is at an outdoor wedding when it is very sunny out. I use flash in order to fill in shadows. For those times, I will normally shoot wide open (typically 2.8) in aperture priority mode, ISO100, and exposure compensation to -2/3 or -1.

By dialing down exposure comp, I can darken the background while allowing my flash to fill in the foreground. Sometimes, I will also need to dial my flash exposure down too. Since my flash sync speed is 1/250, often the camera will automatically compensate by lowering the aperture to around f/5.6. If that isn't acceptable I will turn on the flash's high speed sync mode, but that burns through batteries faster and lowers the recycle time.

What I described is the typical most simple circumstances. The rest of the time, flash is even more complicated.

Without any familiarity with the SB700, if used at manual or auto mode with the camera at manual mode, I recommend you use the lowest ISO setting from the camera (usually ISO 200), the fastest flash sync shutter speed of the camera (1/125s is safe although you might want to try 1/250s), and the recommended aperture size from the back of the flash depending on your distance from the subject (or about f/5.6 for 8-20 ft?). Do a test shot then adjust f/number up if too bright or down if too dark. If you run out of numbers, set back to f/5.6, raise ISO then test all over again.