Okay, I agree about having a hole pre-dug. When trying to dispose of bodies however one cannot forget about lime. Yes our good friend lime will dissolve even the toughest bones in a matter of months. The key is to empty one bag of lime under the body and then completely cover it with the other bag. Then simply fill the grave with dirt and your all done. Also lining your trunk with garbage bags will prevent an unsightly mess. Knives work better than guns because they leave less evidence(no powder burns) and are much more economical, especially if you had planned on repeated slayings.