1. Don't keep it in an ordinary freezer - you'll stuff the freezer completely! An old, already broken freezer is a good way to store dry ice as it's well insulated.
2. Obviously, make sure you're using/storing it in a well-ventilated area....
3. Again obviously, proper safety precautions when handling it - gloves and long sleeves, I had a classmate at drama school who managed to overbalance into some dry ice (he was under a bed where the ice had to appear from, it's a long story!) and he had some pretty nasty burns on his forearms.
4. Everyone else will want to play with it. There are so many fun things you can do with dry ice - in a soft drink bottle with some warm water for a very loud bang, in the toilet with some dishwashing liquid, in a local park fountain - so be prepared for this!
5. Don't let anyone put it in their drink, the possibility of it all going wrong is a bit high for my liking....
6. The water doesn't actually need to be at 100 degrees (Celsius) for the dry ice to work; after much experimentation, we discovered that 60 degrees C was enough to give us really good dry ice coverage for the entirety of Javert's Suicide in Les Mis - which is quite a long ice drop, we were dropping about 15kg of ice for that scene. If you need a really long drop then a higher temp is good, but it doesn't have to be boiling. Do be aware that 60 degrees is the point where Legionnaire's Disease is killed off, so you want to go at least that high.
If any of this is teaching you how to suck eggs, I apologize!