you want an oxygen rush, dont hyperventilate.

just breathe deeply and slow. exhale all air, flex your muscles and push it out, and inhale slowly through your nose, untill yo ucant inhale any more, and then take small gulps, using your throat to 'swallow' the air down. it will want to explode out at this point, because you are taking more than your fill, you begin to stretch your lungs. take a good deep breath like this, and hold it, push it down to your stomach, and you should begin to feel disoriented.

it also works if you need a quick 5 second buzz at any time, and it's perfectly legal! what are they gonna do, arrest you for breathing too much? haha.