How to take a light reading on a nikon D80?

This is pretty embarrising as i should know, but I don't and i feel stupid to ask my teacher! How do i take a light reading on my Nikon D80 i'm on a photography degree and my teacher keeps talking about taking light readings with your camera. Really need help with it, thank you!

Put it in 'P' Program mode.
Then press the shutter down half way, and the camera's metering system will read the light in the scene, and attempt to automatically expose correctly for it.

Ask your instructor. That is why they are there.

Walk up to them with your camera in your hand and ask him/her what they mean and how you do that with your camera

OR

Look on page 52 of your user manual

The light meter may not show up in the viewfinder in P, A or S modes (ie any Auto type mode).In Manual (M) it will be definitely in the viewfinder and/or on the LCD display.

It'll look something like this;

- I--I--I--I--I +

with a zero over the middle. There will be a flashing line or cursor indicating whether the reading is towards the + (overexposed) or - (underexposed) side of the scale.

You adjust the aperture, shutter speed (or ISO) or any combination of those 3 to either increase or decrease the light until the cursor is on the 0 mark.

That will then give you a shutter speed/ISO/aperture combination.