Common mistakes
The root ends in و or ي, and the endings themselves change. Three patterns cover it: دَعَا يَدْعُو, رَمَى يَرْمِي and نَسِيَ يَنْسَى.
صَلَّوَ → صَلَّى Past: heصَلَّوَتْ → صَلَّتْ Past: sheصَلَّوْتَ → صَلَّيْتَ Past: you (m.)صَلَّوْتُ → صَلَّيْتُ Past: I