How do I get an object to stay put when keyframing child of constraint influence? I am a new animator doing some Minecraft animations. One problem I ran into was that when I keyframed influence at 1 and next frame at 0, it moves drastically when I move it to 0. Is there a way to stop this from happening? 

Before I set it to 0 (sword):


After I set it to 0 (the sword moves drastically):
You animated the "influence" on your "Child of" constraint. On frame 0, it was set to Influence of 1.00, but then its influence goes all the way to 0.00 at frame 1. 
This means that you must have accidentally animated the influence from 1.00 to 0.00 in the animation. So, just reset the Influence value back to 1.00 at frame 1.