Spare tires?

I'm doing a presentation on changing tires and tire maitenance, but I'm not the BEST mechanic, and I have to have this presentation ready by wednesday. I'd like to know exactly WHY it's dangerous to drive more than 30 miles on a donut tire, WHY the lug nuts must be tightened in a star pattern after you replace the flat tire, WHY the tires must be rotated at a suggested 5,000 miles, and any other tidbits you'd care to share with me.