"So is it best for each frame to be a keyframe?" Absolutely not. Keyframes are points in time when something significant happens - a motion starts or stops. Once you've got those keyframes in, you add only as required to make the motion "flow" the way you want it. Depending on the complexity of what you're animating, how realistic you want it to be, and the timing , you may end up with a bunch of keyframes. The fewer keyframes you have the easier it will be to keep track of what's what. The Graph Editor helps you visualize how much change is going on and how smooth, or natural the motions is. You can add or subtract keyframes there as well as change them to different types.

Before they made me they broke the mold!
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