Arabic Language and Literature (Grammar, Morphology, Rhetoric)
Grammar (Nahw)
Know the three parts of speech: ism (noun), fi'l (verb), harf (particle). Master case endings (i'rab): raf' (nominative), nasb (accusative), jarr (genitive), jazm (jussive). Know the types of mubtada' and khabar (subject and predicate), and the fi'l tenses: madi (past), mudari' (present), amr (imperative). The trap is mistaking a harf jarr (preposition) for a noun, or ignoring that a preposition forces jarr on the following noun.
Morphology (Sarf)
Know the root system and the awzan (patterns), such as fa'ala, fa''ala, and istaf'ala. Know the difference between mujarrad (unaugmented) and mazid (augmented) verbs, and the derived forms like ism fa'il (active participle) and ism maf'ul (passive participle).
Rhetoric (Balaghah)
Distinguish tashbih (simile), isti'arah (metaphor), and kinayah (metonymy). Know majaz (figurative usage) versus haqiqah (literal usage). Know the three branches: 'ilm al-ma'ani, 'ilm al-bayan, and 'ilm al-badi'.
Worked rule of thumb
When parsing a sentence, find the verb first. A verb governs its subject in raf' and its object in nasb. Example: كَتَبَ الطَّالِبُ الدَّرْسَ - the verb is kataba, the subject at-talibu is in raf', and the object ad-darsa is in nasb. This single check resolves most parsing questions.