Allah: not Allaah · use جل جلاله (not SWT) · capitalize pronouns He Him His We Our You Your · Ar-Rahman (hyphen).
Prophet Muhammad → ﷺ (not SAW/PBUH). Capitalize "Prophet"; add (AS) after prophet names: Adam, Nuh, Ibrahim, Isma'eel, Ishaq, Ya'qub, Yusuf, Musa, Harun, Dawud, Sulayman, Yunus, Isa, etc.
Companions: add (RA) — Abu Bakr RA, Umar RA, Uthman RA, Ali RA. Angels: add (AS) — Jibreel, Mikaeel, Israfeel, etc.
Terminology: Quran (not Qur'an), Surah (not surat), Ayah/Ayat (not Ayaat), Tafsir (not Tafseer), Shaykh (not Sheikh), Imaan, Salah (not salat), Zakah (not Zakat), Du'aa, Da'wah, Akhirah, Wudhu, Fardh.
Greetings/dhikr: Assalamu alaikum wa rahmatullahi wa barakatuhu · insha'Allah (not inshaAllah) · SubhanAllah · Alhamdulillah · JazakAllahu khairan.
Places: Makkah, Madinah, Madyan, Ka'bah, Qiblah, Al-Hudaibiah. Names: Fir'awn (not Firaun), Bani Isra'eel, Thamud.