With the planer blades and rollers off, raise or lower the bed so that your workpiece just brushes the rollers but can still be slid in and out of the machine with a little friction.
Remove your workpiece and bring the bed up three full turns of the handle (3/16").
With the planer hooked up to dust collection, turn the blades and rollers on. I recommend starting at 50% roller speed.
Pass your workpiece into the rollers, making sure to stand to the side of the machine rather than right behind it.
Slowly raise the bed as your workpiece passes through (this is actually according to the manual), stopping as soon as you hear the blades start to bite.
Without raising the bed, pass the workpiece through the planer again.
Raise the bed again and pass your piece through, this time without raising the bed while your piece is in the machine.
Repeat step 7 until you have a smooth surface on one face.
Once one face is smooth, flip the board over and repeat step 7 until the other face is smooth. As long as you didn't start with a twisted, cupped, or bowed piece, you should now have two parallel faces.