Different speeds, different configurations, and moving between them climbing and decending and straight and level.
Here's a great exercise. Trim for cruise. And when I say trim, I mean sufficient for hands-off flying. Don't trim to reduce stick forces, trim to eliminate them altogether.
Now close the throttle. Let the speed decay to just above stall speed. Then open the throttle again and let the speed increase to "redline" speed - the highest speed you can get in level flight without the engine overrevving. Close the throttle again and let the speed decay to just above stall speed. And so on and so forth.
During this, make sure the ball is absolutely dead center throughout. And make sure you maintain altitude exactly - watch the altimeter like a hawk and don't tolerate even 10 feet of deviation. After maybe ten or so cycles, see if you can do this without watching the ball and altimeter, just by aircraft feel alone.
For added fun, you can also incorporate flap extension and retraction in your routine.
And be gentle on the throttle. Don't slam it open or closed. If you take about three seconds from closed to open and vice versa your flying will be much smoother. For proper engine operation and the prevention of shock cooling, you should even take much longer than that.