Never may either precede or follow a tensed auxiliary.
The ordinary position, as you know, is after the auxiliary.
He will never agree.
I have never liked sushi.
She will never be mine.
But in parallel clauses like this, never is usually placed before the auxiliary; this throws the stress onto the auxiliary and thus emphasizes the contrast in tenses.
He has not agreed, and he never will agree.
She is not mine, and she never will be mine.
I don't like sushi, and I never have liked sushi.
Note that the parallel clause need not occur in the same sentence; the speaker may ‘pick up’ a phrase to parallel in the previous sentence.
A: John has never agreed to proposals of this sort.
B: And he never will agree to them, trust me.
The displacement is not obligatory. When the second clause is full, never may occupy its normal place; in this case, never bears the stress.
okHe has not agreed, and he will never agree.
okShe is not mine, and she will never be mine.
okI don't like sushi, and I have never liked sushi.
But when the auxiliary stands alone, with what follows it (the complement and/or the main verb) ellipted, the never must precede the auxiliary.
okHe has not agreed, and he never will. ... but
∗ He has not agreed, and he will never.
okShe is not mine, and she never will be.† ... but
∗ She is not mine, and she will never be.
okI don't like sushi, and I never have. ... but
∗ I don't like sushi, and I have never.
∗ marks a usage as unacceptable
† Note that in clauses where the lexical verb is be acting as a copula (linking verb), the be cannot be ellipted; these are both ungrammatical:
∗ She is not mine, and she never will.
∗ She is not mine, and she will never.
But when the lexical verb is be without a complement, in the sense “exist, occur”, it can be ellipted, and the rules I describe above apply:
okThis must not be, and it never will be.
okThis must not be, and it will never be.
okThis must not be, and it never will.
∗ This must not be, and it will never.
Let's take a closer look at exactly what we're dealing with. Firstly let's ditch the preposition phrases which tell you when something happens, for example on Tuesdays. These aren't really expressions of frequency. Teach these with other temporal preposition phrases such as on Tuesday or at Christmas. Also notice that only the context will tell you whether on Tuesdays implies that the occurrence is actually a weekly event. [For what it's worth preposition phrase Adjuncts (read Adverbials, if you really must) usually go at the end of the sentence, but can also go at the beginning. They never go in the central position]
Secondly, we need to ditch expressions that tell us how much something is done. These may tend to imply frequency, but this is just an implication. These are not real frequency expressions. They are expressions of degree or quantity. Notice that someone who swims a lot, may not swim very often. They may spend one month every year for example, swimming eighteen hours a day at some special event and then not swim for the rest of the year. So expressions like a lot, a bit, much and so forth are not part of what we are dealing with.
Right, so that leaves us firstly with specific frequencies that tell us exactly how frequently something happens. These are usually noun phrases or adverbs derived from nouns. These usually go at the end of the sentence:
- She plays football every day
- She eats custard twice a week.
- The meetings occur daily.
They can also go at the beginning:
- Twice a week she plays football.
They cannot go in the post auxiliary position:
- *She three times a year goes to Spain.
And then, secondly, there are those relative, notional frequencies that are vague and not clearly specified (unless they are absolutes like always or never). These are always expressed by adverbs. The favoured position for these is the post-auxiliary position. Some of them can also go at the beginning or end of the clause, but it's important that students understand that the normal, unmarked position is the post-auxiliary one. These adverbs include always, usually, normally, often, sometimes, rarely, seldom, hardly ever and never.
- She is always eating pizza.
- Elephants never forget.
- I am hardly ever wrong.
- We have rarely seen such fine baboons.
- You can sometimes hear them whistling.
If your students are unsure about where the post auxiliary position is, it's the place that you would put the word not:
- She is not eating pizza.
- Elephants (do) not forget.
- I am not wrong.
- We have not seen such fine baboons.
- You can't hear them whistling.
It does not matter if these expressions have more than one adverb in them. When this happens it is because the first adverb is modifying the second:
- I am almost always late for class.
- I have hardly ever eaten rhubarb.
- I am most often the last guy to leave the party.
Note:
It is of great benefit to students to understand that BE is nearly always an auxiliary verb, even if there is no following verb. It also certainly makes it much simpler teaching where in the sentence adverbs of frequency should go.
Hope this is helpful!
Best Answer
If the verb is intransitive (ie there is no object), an adverb of manner is usually placed after the main verb. In literature or poetry it can also be placed before the verb at the start of the main clause.
If the verb only has an indirect object (ie there is a preposition between verb and noun, the adverb normally goes after the main verb, though it can also go at the end of the sentence: this is common when using a long adverbal phrase.
When a verb has a direct object, you never put an adverb of manner between the verb and its direct object: instead, you put it at end of the clause, or before the verb.
Looking at your two sentences, carefully is placed before the verb for literary effect, and nervously is placed after the verb because this the is normal position for a verb with an indirect object (the window).