I learned how to make one when I was in school and if you ask me to make one now, I doubt if I will be able to remember how I used to do it. So I did a little searching and found lots of resources. One even expected me to sign up for their pro membership to view larger images of the steps! Forget it.
Thanks to WikiHow.com, I will be able to pass on valuable information to my son and the legacy will live on. Bombs away!!!
P.S.: Oh, if you want your project to sound less devious or destructive, you may want to refer to it as an 'Origami Balloon.'