Some Dutch grammar rules apply so broadly that mastering one rule unlocks many patterns. The most powerful: the V2 rule. In Dutch main clauses, the verb always occupies the second position. This means if any element other than the subject starts the sentence, subject and verb invert: Gisteren werkte ik (Yesterday I worked). Knowing this one rule lets you construct correct sentences with any time adverb, place adverb, or fronted object.
The de/het rule with diminutives and plurals: all diminutives take het regardless of the base gender (het huisje, het boompje, het meisje). All plurals take de (de huizen, de bomen, de meisjes). So for plurals and diminutives you never need to look up the article. For adjective inflection: before het-words with an indefinite article, the adjective gets no -e ending (een groot huis); in all other cases, it gets -e. These two cases cover every adjective position.
The past tense shortcut: the t-kofschip rule determines whether a regular verb takes -te or -de in the past. If the stem ends in t, k, f, s, ch, or p (the letters in t-kofschip), use -te/ten; otherwise use -de/den. Werken → werk (stem) → k is in t-kofschip → werkte. Leven → leef (stem) → f is in t-kofschip → leefde. Wait — f is in the rule, so leefde. Actually this is one learners always double-check. The rule is: the consonant that sounds at the end of the stem, not the spelling. Practice with at least 20 verbs before trusting your instinct.