In addition to what the others have said, you may find it useful to note that the words "ISO/AUTO" will be flashing in the viewfinder when auto ISO has engaged and is setting an ISO value different from your preferred one. Otherwise, the words remain non-flashing.
Also, I choose "Show ISO sensitivity" in menu d3, which allows me to keep an eye on how much the ISO is changing while auto is engaged.
OK, thanks all, I wasnt sure whether it meant that it was out of range or something similar. Red to me means a warning.
Along those lines if using auto iso is there anything in the viewfinder that would let you know that a scene cannot be correctly exposed with the min /max iso/shutter speeds you have selected in the menu ?
I don't think you get a warning because if the scene cannot be correctly exposed within the bounds of your settings, the camera will exceed your setting. There is a very oblique discussion in the D7000 owner's manual under Auto ISO Sensitivity Controls, but Fellow Nikonian Darrell Young has an excellent description in his book "Mastering the D7000". In short, Darrell's explanation - shooting in programmed or aperture priority. The camera will keep the ISO as low as possible until it hits the minimum shutter speed you set in the ISO sensitivity settings. It then starts increasing the ISO until it hits the max ISO value you set. If there still not enough light, it will then decrease shutter speed below the min shutter speed you set to try and achieve proper exposure. If you don't have a copy of Darrell's excellent book, I'd recommend you get a copy. I read it from cover to cover when I got it and find myself refering to it frequently. Enjoy your D7000.
"Nothing can be recognized without light and shade. It is only through the eye, the window of the soul, that we can truly understand the complex workings of nature." - Leonardo da Vinci