I have a camera set up, and everytime I make a hold keyframe to animate, it automatically adds a bezier to it. That keyframe was copy and pasted from the previous one..but in between them it's animating. I've encountered this problem before, but can't remember how to fix it..sadly.
Don't forget about the Graph Editor. You can remove any motion between the two Hold keyframes by using it.
Hold keyframes can be a bit tricky, but they're worth it sometimes. For example you can have a combination Ease In/Hold keyframe, followed by a Hold/Ease out keyframe. Between the two, the motion is rock-solid.
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There is also a preference you can adjust to change the way future keyframes are set:
Preferences > General > Default Spatial Interpolation to Linear
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In addition to the other tips already provided I'll mention that you have 2 great options for adjusting both kinds of interpolation to get exactly what you want.
Dave already mentioned the Graph Editor, which is fantastic for adjusting Temporal Interpolation. You can use this to adjust how quickly animating properties accelerate/decelerate.
If you're looking to adjust the Spatial Interpolation then I recommend using the Pen tool to adjust motion paths directly in the Comp Viewer. Every keyframe in the comp viewer appears slightly larger than the intermediate frames. You can directly adjust the bezier handles of keyframes with the Pen tool (just like mask vertices) you can even add or remove keyframes (just like mask vertices).