Writing is spelled w-r-i-t-i-n-g, pronounced /ˈraɪtɪŋ/. It is the -ing form of write: the silent e drops and the t stays single. Not writting; /ˈraɪtɪŋ/ has one /t/. Righting sounds the same but means correcting.
I am writing an email now. - Writing helps me remember new words.
He was ___ notes during the lecture. Pick writing: the t stays single after dropping the silent e of write.
Her ___ was hard to read. Choose writing here too, the only spelling for composing text. Do not pick righting, which means correcting something and changes the meaning.
They are ___ a report together. Go with writing: one e has dropped, and the -ing ending follows the single t.
Feedback rule for all three: if the sentence is about composing text, the letters are w-r-i-t-i-n-g, pronounced /ˈraɪtɪŋ/.
Writting is the misspelling to resist. English doubles consonants to mark a short vowel before them, as in sitting, but here the vowel is the diphthong /aɪ/ in /ˈraɪtɪŋ/, so the single /t/ needs no double letter.
The stress in /ˈraɪtɪŋ/ sits on the first syllable either way; the spelling error is about the single /t/, not about emphasis.
One meaning restriction: this form covers composing text only. Its homophone /ˈraɪtɪŋ/, spelled righting, means correcting a wrong, so context, not sound, settles which spelling you write.
She is writing her essay tonight. - The righting of that injustice took years.