tickles, teasing and taunts
red indian (hey, your name doesn't have anything to do with "Injun' Joe", the famous, ticklish native american of cartoon fame, does it??)
I can't comment on the physical aspects of making someone more ticklish, but I've thought a lot about psychological techniques. A couple weeks ago I responded to a post asking about ticklishness, part of which I quote below. I believe the key is creating the "playful attack" feeling within the ticklee and is done mainly with words and gestures. It is related very much to what Mistress Mia describes in her post about "taunting and agonizing me". You have to make the ticklee feel you are really going to "get" her or him. This is why all kinds of taunts and teasing (even "kitchie koo") can be massively effective as well as things like blindfolding someone, holding the person in a more vulnerable position, or wriggling fingers at them.
This is what I wrote on the subject--
Tickling is a kind of playful attack which causes the recipient to experience two different strong emotions at once. On the one hand, she or he is being "attacked" which creates some fear or anxiety, but at the same time, the ticklee knows it is not for "real", that the tickler is not really trying to hurt her or him. This living on two contradictory levels at once generates laughter as a release.
Being ticklish depends on the "ability" of the tickled person to perceive the touches as a (mock) attack. Some people will just never feel that having fingers moving around on the bottoms of their feet could really "get them". But the same person having one little pinky move closer and closer to her ribs or underarms could really feel "threatened" and out of control.
Control, or lack of it, is a key element. If you feel perfectly in control there is no threat, not even a playful one. This is why a lot of people say "I'm not ticklish, unless someone tickles me by surprise". It is not the "surprise" that makes them ticklish, it is that they were off guard and felt more vulnerable. Now they can sense the "attack".
The fact that ticklishness is part of a psychological "contest" is reflected in this: Many people are not so ticklish if they feel they can "get away" from the tickler whenever they want, but if they are "trapped" or "in your power", they go crazy. In other words, the very same physical sensations are experienced in very different ways emotionally. The feeling of being "in someone's power" can be established with words as much as with restraints.