Tickling is caused by applications of light sensation on the surface of the skin. This can lead to giggling, heavy laughter, and uncontrollable jerking of the limbs and torso. The soles of the feet are very sensitive parts of the body when stimulated with light pressure. The nerve fibres around these areas are connected to the ones for pleasure, pain, and touch stimulation -- all of these combined along with the element of surprise cause tickling. Tickling is classified into two types: the knismesis -- which is a light tickle that may or may not produce laughter; and the gargalesis -- which is a little bit more heavy than the knismesis tickle and always produces a laughter response. There is really more to just plain tickling. Tickling promotes mutual laughter that bonds and strengthens emotional relationships. It enhances closeness by merely using the fun side of tactile sensation.
Use the claw. Pin both the ankles of your partner and lightly scrape the tips of your finger over the soles. When she starts giggling, increase the intensity by stroking your fingers all over the surface of the soles. Do this until she is almost out of breath from laughing, or when she tells you to stop.
Get a feather. Facing the soles of her foot, lightly brush the feather on her soles in just one direction (up and down). When she starts giggling, increase the intensity of your tickling by stroking the feather all over the surface of her feet, including the back of her toes. Continue doing this until she tells you to stop.
Use a soft bristled brush. Using a body brush with very soft bristles, apply a light up and down strokes on her foot. As she giggles, increase the level of your tickling by stroking the brush all over the surface of her soles, including her toes. Keep on going until she tells you to stop.
Try to not overdo your tickling. A general rule for tickles is to cease when the tickled person tells you to stop.