Three positions are fixed and the rest of the sentence is yours to move. The subject comes before the verb, nothing at all comes between the verb and its object, and a direct question puts the auxiliary in front of the subject.
Learn those three and you can put a time expression almost anywhere you like without ever being wrong. Break the second one and you will still be understood, every time, for the rest of your life, which is exactly why it is the one that never repairs itself.
Eight rules that decide where a word goes
- subject, verb, object, and English will not let you move them, because it lost the endings that would say which was which.
- adverbs of frequency go before the main verb but after be: she always arrives late and she is always late.
- I often go and I go often are both acceptable, but the first is neutral and the second puts weight on the frequency.
- a lovely little old French wooden table. Adjectives follow a fixed order: opinion, size, age, origin, material. Native speakers cannot state the rule and notice instantly when it breaks.
- place before time. I went to Cork on Friday, not the other way round, which is the reverse of the German habit.
- turn it off, not turn off it. A separable phrasal verb splits around a pronoun and may split around a short noun.
- Never have I seen. A negative adverb at the front forces the subject and verb to swap, the one place English still inverts outside questions.
- Do you know where he is, not where is he. An embedded question drops question order, and this error survives longest at advanced level.
The three that break a sentence, and the fourth that only marks you
The first two are quick. A subject in front of a verb is what tells an English sentence who did it, and the object sits immediately behind the verb with nothing wedged in between. The third is the one with a trap in it: a direct question inverts, and an embedded question does not. Where is the station is a question; I do not know where the station is contains one and keeps ordinary statement order, and a learner who has drilled inversion hard will invert both.
The fourth is different in kind. English orders its adjectives, and a native speaker who has never heard the rule obeys it anyway: opinion, size, age, shape, colour, origin, material. A big old wooden table is invisible and a wooden old big table stops the reader without their being able to say why. Getting it wrong breaks nothing and misidentifies you in four words, and because nobody can state the rule, nobody corrects it.
What is genuinely free, and what moving it buys
The free half is larger than most learners expect and it is not free of consequence. On Friday I called him and I called him on Friday are both correct and they are about different things: the first has made Friday the topic and the second has made it the news. English gives you the front of the sentence to say what this one is about, and the back of it to say what is new.
Where a frequency adverb sits is fixed in a smaller way: always, often and never go before an ordinary verb and after be, so it is I always arrive late and I am always late. That much is a rule. Whether you front the whole adverbial for emphasis is not.
Where it stops: an adverb wedged between the verb and the object
I like very much this film. I speak fluently English. He plays well football. This is the single most persistent word order error in English, and it survives at every level, including in people who write publishable prose otherwise.
It lasts because two things protect it. Nothing is ever misunderstood, so no listener repairs it. And in French, Spanish, Italian, Persian and most of the languages the average learner arrives from, that slot is perfectly legal, so the sentence feels right from the inside. The fix is not a rule you have not met. It is noticing that you already know the rule and are not applying it under speed.
Settling it without an argument
Google Books Ngram Viewer plots how often a phrase appears in printed books over time, free and without an account, and it settles this class of question in ten seconds. Put in speak English fluently against speak fluently English and one line runs across the chart while the other sits flat on the bottom. It replaced an argument about which one sounds better, which used to be won by whoever was more confident.
Its limitation is the whole reason to state what it is for. It only knows printed books, so a phrase that lives entirely in speech comes back flat too, and a flat line is evidence that nobody printed it rather than evidence that it is wrong. Use it on word order, where print and speech agree, and not on anything colloquial.
What it looks like when it goes wrong
Four sentences cover almost all of it. I like very much this film, from the wedged adverb. Always I am late, from fronting an adverb that belongs inside. I do not know where is the station, from inverting an embedded question. And a wooden old big table, which breaks nothing and is noticed instantly.
Only the last of those is invisible to the person saying it. The other three are all recoverable the moment somebody points at them, which is what separates them from the errors that survive years of study, and why they stick, and all of them sit under the rules that decide what a sentence is allowed to mean.
The interesting half is the free one, and it leads somewhere specific. If the front of a sentence is where you say what it is about, then you sometimes need a noun there that did not do anything, and English has one device built for precisely that: when what was done matters more than who did it. Doing any of this at conversational speed, rather than while writing, is a separate problem: getting from correct sentences to an actual conversation.