I myself I don't have a QDII however there are many "true-isms" that apply to all metal detectors no matter the brand or model. Nothing substitutes for "stick time". The best thing you can do is to get out and use the detector. Don't be tempted to crank up the sensitivity to the max as this usually ends up giving false or phantom signals. Follow what the manual says on setting sensitivity settings for at least a little while. Sames goes for the discrimination setting, follow the manual. Dig everything for a little while just to see whats in the ground, you may be surprised. Eventually you will learn what your detector is telling you what is in the ground. Above all else take your time, be safe, and have fun. I know you will get much more specific info from the experts that have the same machine as you do however some of the basic info needs to be repeated from time to time. Good luck and HH. I look forward to your posts of finds in the future.
Jeff