'sein' and 'haben' in the simple past conjugate as war/warst/war/waren/wart/waren and hatte/hattest/hatte/hatten/hattet/hatten, and are used more commonly than the perfect tense even in everyday speech.

Modal verbs in the simple past drop the umlaut (if any) and take regular-verb-style endings: können→konnte, müssen→musste, wollen→wollte, dürfen→durfte, sollen→sollte, mögen→mochte.

Many strong verbs have an irregular past participle (with a stem-vowel change, sometimes a consonant change too), which must be memorized like vocabulary.

In a German main clause, the conjugated verb is always in position 2; if something other than the subject is fronted, the subject inverts to after the verb.

'weil' (because) introduces a causal subordinate clause and pushes the conjugated verb to the end of that clause.

'dass' (that) introduces a subordinate clause complementing the main verb (think, know, hope...), pushing the conjugated verb to the end of the clause.

'wenn' introduces a subordinate clause of condition or repeated time, pushing the conjugated verb to the end of that clause.

The comparative adds the ending -er; the superlative uses 'am + adjective + -sten'. Many one-syllable adjectives also add an umlaut.

The dative is the case of the indirect object (the receiver); the article changes der→dem, die→der, das→dem, plural→den.

A group of German verbs (helfen, gefallen, gehören, danken, antworten, glauben, gratulieren...) always take a dative object, not an accusative one.

The 9 two-way prepositions take the accusative when answering 'wohin?' (movement) and the dative when answering 'wo?' (static location, already covered at A1).

Reflexive verbs take a reflexive pronoun in the accusative (mich, dich, sich, uns, euch, sich), expressing an action the subject performs on itself.

Some reflexive verbs use the reflexive pronoun in the dative when the sentence already has another accusative object (often a body part/one's own belonging).

Many verbs/expressions (vergessen, versuchen, Lust haben, wichtig sein...) are followed by an infinitive clause with 'zu' right before the infinitive, at the end of the sentence.

'sollen' expresses advice/a request from someone else; 'mögen' expresses general liking, different from 'möchte' even though they share the same root.

An adjective before a noun and after a definite article (der/die/das) takes the ending -e or -en depending on gender/case/number.

Possessive determiners inflect like the indefinite article (ein/eine) according to the case and gender of the noun, including in the dative and accusative.

'wegen' (because of) and 'trotz' (despite) take the genitive, with the article changing der/das→des (+s/es at the end of the noun), die→der.

Future I = 'werden' (conjugated) + main verb in the infinitive, at the end of the sentence, used to talk about the future or make predictions.

When asking about a thing/matter (not a person) that goes with a preposition, use 'wo(r)+preposition' (worüber, womit, wofür...) instead of 'preposition + was'.

Ordinal numbers add '-te' (4-19) or '-ste' (from 20) to the cardinal number, and are used to say dates.

'möchte', 'hätte gern', 'würde + infinitive' are fixed expressions using subjunctive II to phrase requests/wishes more politely than the direct form.