What is the most efficient way to remove the popcorn from my ceiling? Are there any tips for preventing it from spreading throughout my house (ie. creative use of a shopvac?)

 

mist it thoroughly with water,scrape with a plaster knife, wait for it to dry(overnite) and sand with 100 grit

 

Hello towanda & welcome to the forums. Mudder's has got you all fixed up here with good advice.
As far as keeping it out of the whole house, put up some plastiic sheeting, over doors leading to the rm, it'll help but won't eliminate it. Be prepared to give everything in the place a good dusting when the project is complete.