i'm so glad you asked! i look for descriptions, they make the story for me. i hate it if i never find out what the ticklee is wearing, especially on their feet. i need to visualize whether their bare feet are being tickled or if they are getting tortured through nylons! lol, so yeah i would have to go with details details details on this one. 😛
I gotta agree with Dig Dug Dog, plus I also like when the story is quite long and the tickling happends near the very end, I also look for the certain tickling tool and techniques that are used on the lee, and I must be able to visualise it in my mind, and one important thing is that it has to be realistic and believable.
I know im an oddball for saying this, but I voted for characters. No doubt all the things you mentioned are important for a good story, but I find that especially in fanfic there is a lack of sufficient character development. Sometimes the person writing the fanfic doesn't even know much about the celebrities they describe, and to me this cheapens it. There is nothing more titillating as a fan than to hear details about the celebrity that I know are in fact true. It makes the fantasy more convincing and captivating. Just my humble opinion.🙂
I agree with all of the above, and I would like to add: motivation. It doesn't always have to be something like revenge, but knowing a good reason why the ticklee's getting it or how the whole thing came about often intensifies my enjoyment. It gives me that, "omg, now I know she/he is really gonna get it good!" feeling.