If you're doing smooth animation, make sure you keep 3 things in mind:
1. how fast the animation will be playing can ruin the animation, so try to avoid making it complicated.
2. spacing between keyframes should stay even-ish to keep it from being choppy.
3. copy the first keyframe, and put it at the end. It'll bring the animation back to a somewhat reasonable point. EDIT: This should only be done for animations that loop
Do this, and you should end up with something resembling smooth animation.