One rule explains more of Japanese grammar than any other:
the verb always comes last.
English follows Subject-Verb-Object (SVO) order: "I eat bread." Japanese follows Subject-Object-Verb (SOV) order instead: "I bread eat" — 私はパンを食べる.
Because particles (は, を, に, etc.) mark each word's grammatical role directly, word order in the middle of the sentence is actually fairly flexible — you could say パンを私は食べる and still be understood. But the verb almost always stays at the very end. If you remember only one structural rule, make it this one.
Many Japanese sentences follow a topic-comment pattern rather than a strict subject-verb pattern: は introduces what the sentence is about (the topic), and everything after it is a comment on that topic.
Once a topic has been established, Japanese speakers routinely drop it from later sentences rather than repeating it — a major difference from English, where subjects are almost always restated.
In English, a relative clause usually follows the noun it describes: "the book that I read." In Japanese, the modifying clause comes before the noun instead:
This "modifier-first" pattern shows up everywhere in Japanese, not just with relative clauses — adjectives, and description of any kind, consistently come before the noun they describe.
Three habits carry most of the weight: keep the verb last, use は to set up what you're talking about before commenting on it, and put descriptions before the noun they modify. Everything else in basic Japanese grammar builds on top of these three patterns.