Make yourself comfortable. Then use the tip of your finger to gently, and slowly, push back a small section of the pedal disk. Once you have a small section, about the size of the tip of your finger, peeled back, SLOWLY start working your finger under the anemone. This can take a while. Just apply enough pressure to cause the anemone to let go. Don't try to rush things and start prying the anemone off.
If the anemone is stuck to both the bottom of a rock and the glass on the bottom of the tank, the only thing I have found to work, is to lift the rock slightly and place something under the rock to keep it up. Just lift the rock high enough that you feel the anemone holding it down. The next day, lift it a little more, and brace it up. Keep doing this until the anemone lets go of one or the other, or you can reach your hand under the rock and start working it loose like above. Just be very careful not to lift the rock to much at one time.
I've tried power heads and ice cubes. Neither one will work on my haddoni.