Ask the instructor to set the aircraft up in a stable descent. Look directly ahead of you and take in the picture. Particularly how far the coaming is below the horizon. (There may be a rivet or something in the frame supporting the windshield which makes a good marker. When I was doing some Vbg testing I actually put some sticky tape on the windshield, aligned with the horizon, for the attitudes I needed.)
Do the same for level flight and a proper climb. Remember the picture. Also note the engine sound.
Now take back the controls. When transitioning from one phase to the other DO NOT look at any instruments. None whatsoever. Just look straight ahead at what you see outside. Look at the horizon and set its position with reference to the aircraft reference points, such as said rivet. Look at a specific object dead ahead. If it moves left or right during power changes, and the wings are level, you need to work the rudder. For cruise, set the engine RPM by sound.
And once again, don't look at the instruments. None whatsoever. It may sound strange, but it's a lot easier.
Remember Power + Attitude = Performance. You set the right amount of power and the proper attitude, and that will give you the desired performance. Instruments like the DI, ALT and V/S are only there to fine-tune the attitude. But don't chase the instruments with the attitude or power - it only leads to oscillations.