ok so, this is coming from someone who's been writing t-fics over the past 6 years (which is so fucking crazy to think about so let's move on-) and this is in NO way a standard guide to writing t-fic. like all fanfiction, there are 0 rules to what you should/shouldn't do, and as long as you're having fun, that's all that matters! but if op or anyone else is curious, here are some things i came up with that might give another perspective on how to spice up your t-fic game:
read t-fics/authors you like and figure out why you like them. for me, verbal teasing was always the big thing i looked for when looking for t-fic, so of course when i started writing my own t-fic, that's what i tried to emulate in my own writing. not because i thought it was what was popular (altho i am lucky in that fics with a lot of teasing are quite popular) but bc it was earnestly the kind of thing that i would want to read. just have fun with it! (i also recommend reading t-fic for fandoms you're not in, just to get some variety/perhaps find new authors you like, but i understand not everyone wants to do this lol).
start in media res while you're writing/drafting. this is something i Need to try to do more, because i also get bogged down in my prose/exposition before i feel like i can "start" the tickling. you can go back and add plot or context or emotional resolution later (if you want to- again, only write the things you'd want to read!) but if you're in the mood for tickling, then write TICKLING, not the explanation for why your characters are in this exact scenario. let yourself do the fun part first! (also don't feel like you have to make every fic into a full narrative. if you write a 150 word tickling scene that you like but you don't know how to make it a longer fic, then just post the 150 word tickling scene by itself!)
break down your paragraphs into shorter, easier-to-read chunks. this is good writing advice in general imo, but i find it ESPECIALLY useful in making tickling actually feel like a whole scene in and of itself, not just an addition to a larger scene. it lets the tension and anticipation build up more. it also allows you to more easily insert moments of internal narration between lines of dialogue (and internal narration is where SO MUCH of the best t-fic character work happens). basically just follow the standard sort of guideline for when to change paragraphs- when a new person or topic enters the scene, when the time or place shift, when someone does an action that changes something, and whenever there's a new line of dialogue.
figure out which moments to drag out, and which to fast forward. writing t-fic can be so difficult if you try to think about it in terms of how much time the tickle scene would actually take. like think about all those fics that mention tickling someone for 30 minutes- do you know how long 30 minutes actually is? now, this is NOT to say that you shouldn't write fics where people get tickled for a long time, bc again, that's literally the fun part of it lol. but when you're writing, it's easy to keep the same pacing throughout the entire fic: "X tickled Y. Y laughed. X used this tool. Y begged. X teased them and did this. Y screamed". it makes the timeline of the whole thing just feel odd, meandering, or like it's a dead-end. just like when it comes to other types of fiction writing, try varying your sentence lengths! if there's dialogue, give us certain snapshots of dialogue between the lee/ler, and then go back to narration if you want to indicate that more time is passing. put one moment under a microscope at a time, and show the readers why THIS moment is important for you (the author) to show us.
use physical language as much as possible. not just about different ways to tickle or laugh, but how the lee and ler are FEELING about being in this tickly scenario together. maybe the lee's anticipation manifests through shimmying shoulders, legs kicking out at nothing, fingers scrabbling against the bedsheets. maybe the ler likes to swoop their head low to make the lee feel trapped, or they taunt the lee by showing how casually and easily they can drape their whole body over the lee's, or how they have to hold themselves back from pressing down too hard because they're so excited. it's not just about the actual tickling, it's about the EMOTIONS that the characters are feeling about the tickling.
but also, using a variety of terms for both tickling methods and types of laughter can help to keep your work from feeling uninspired. off the top of my head, different tickling methods can be described as: squeezing, nibbling, scratching, fluttering, mouthing, tracing, digging, plucking, trailing, drilling, squishing, skittering. different types of laughter include squeals, giggles, snorts, wheezes, screams, shrieks, gasps, trills, peals, whines, and groans. similes, metaphors, and onomatopoeia are good too ("the tingles zinged down their spine like a live wire", etc).
read fic or find art that makes you personally feel flustered. trigger your own ler/lee mood until you feel like you will melt and/or explode. then project those feelings onto your blorbos of choice. that's what i do lmao
be unique. and notice, i said "unique" NOT "original". it is virtually impossible to be "original" in the TFB- there are thousands of fics about "X character is grumpy and sarcastic so Y tickles them" (and i will read every iteration of this trope ever dkfjhdjs). don't stress yourself out about if your idea has been "done before". your UNIQUENESS is whatever draws YOU to writing t-fic in the first place. if you want to write 1000 fics about the same character discovering that they're ticklish, then do it! there will ALWAYS be an audience for it! if you write it because you think it's fun, you'd want to read it and you are passionate about it, then the reader will know, and the joy of your fic will shine through.
i apologize in advance if this is super arrogant, but i do earnestly love t-fics and it makes me happy to talk about them DJFHDSJK