閱讀。
找英文讀物(網路上也很多)，閱讀跟您現在工作專業有關的書籍雜誌，包括跟外國客戶互動閒聊時, 可能會用到的東西(這部分當然範圍就較廣了些)。
這是一個人就可以做的，也正是在運用英文(語言上，讀，聽，說，寫，皆為用)。這也可從實際英文當中,，不只獲得您可能馬上就用得到的單字詞之外，也可從閱讀中，獲得跟習慣英語文的句法跟表達方式 (亦即，單字詞之上的，短語、整句的層面)。而且是獲得很容易就能派上用場, 有用的字詞句。
閱讀。
在實際的英文閱讀當中，從上下文/語境來獲得英文單詞，來獲得英語的表達方式，來獲得用完整句子完整表達的方法，同時就其中的一些字詞句，想像您曾在工作中碰上, 也很可能再在工作上會碰到的情境。(而不會如在學校只"學"英文時，有漫無邊際的可能情境)。
這更可讓您跟客戶對談時，或文書往來時，言之有物，而不會是"speak, but say nothing"。
美國的乞丐/流浪漢，英語可能可以講得比您更流利，而且語音很可能就是英語。但，卻當乞丐/流浪漢。您不是。
語言, 絕對不僅僅是語言本身而已。
又，建議您手上放本較完備的語法書，但是莫當成要從頭看到尾的教科書(那是沒有幾個人能撐下來的)。而是當成參考書，在閱讀英文，見到有可能相關的東西時，翻閱相關章節。那會是較為輕鬆自然，輕鬆自然的獲得語法書，所系統性整理的英文規則規律，得到提綱挈領的好處。而這部分。您可到書局查找另外是否有專門介紹 英文五大基本句型 的書籍，不要太厚的 -- 這是英文構句方面，最最提綱挈領的規律。單字不成詞，單詞不成句，語言也至少要是句子的形式，才能完整表達意思，不論是主動表達，或透過別人的句子來被動接收訊息。
依您所述，您目前正是在可以有效率的學習以及使用英語文的環境。語言的有效率 學習 是跟 使用 分不開的。這該是您或很多人，在學生時代所無的環境。特別因為您在工作中用得上，而且是馬上要兌現 -- 現學，就可能可以現用，用了就學得更實在，或就知道哪一小部分沒學真切，馬上補，在下次就可能又用上。如此循環，點點滴滴累積，那會學得更實在，用得更真切。學用相長。這也該是依您狀況, 最有效率的方法了。
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注意到題主在題目說明裡面的最後一句, 以下也針對您這一句 ---
「目前买了一本《牛精高阶英汉双解词典》，没事就翻翻」
語言，以及真正要使用某種語言來言之有物，不是僅靠翻辭典得來的。就如同，您能流利使用普通話，且言之有物的這個能力，絕對不是靠普通話辭典得來。而多是靠在普通話環境當中，不知不覺的吸收。同時使用，以及靠有意識的閱讀普通話書籍讀物，來吸收不只更多的字詞彙，同時用普通話不斷或不自覺的發表(就是使用普通話, 將所獲得的知識，化成語詞句，放入您所發表的語/文當中使用)，而使您自己能言之有物的。
用普通話表達，能流利、能言之有物，是這麼來的。不是靠背字辭典來的。英文英語，亦然。是循同樣的道理，也該循同樣的道理。
語言, 絕對不是單字詞而已。英語/英文, 當然亦如此。
"Words are never used in isolation."
辭典只是佐助，不是主角。若不是從上下文語境當中所獲得的單詞，而光是汲汲於背誦孤伶伶的單詞，不止容易忘記，也很難是有用的單詞。
光背單詞，特別若又僅僅是透過辭典上(勉強對應的)普通話語詞，所背得的英文單詞，很容易會是不知道如何用，而變成沒有用的單詞 (或以普通話語詞習慣去用，誤用而不知，而往往有"Chinglish"現象) － 除了，在學校或在考試上, 或許能多少有點用之外。
然而，若已經離開學校，且面對的就是真刀真槍的實際運用，要使用不只英文還有英語，這是沒有數字來表示成績的考試，但可能會是一輩子的考試。
而關於單詞，早之前曾在 David Chrystal 的一本談語言/Language的書上看到一個章節，有關於語言裡，在意義/meaning表達會有的各種方式，並針對語詞/詞彙方面多所著墨。
是頗為精簡精闢的闡述，而且如同該作者一貫的風格，文字不生澀。我把該本書從書架上翻出來，將該章節繕打放在這裡供參考。並同樣大膽就知乎的版面以及工具，稍作分行分段，以及標點跟字體上(粗體/斜體)的小更動，希望能較方便閱讀。
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"How do we express meaning?"
There is a limited number of ways in which we can organize the resources of a language to do the job.
The chief means are words, sentences, patterns of discourse, and certain aspects of phonology and graphology.
The traditional focus has been on words – vocabulary – but the relevance of other factors is plain when we consider the following examples, each of which introduces a change into the meaning of a sentence.
- We change a word: "I see the starship" vs. "I see the alien".- We change the grammatical structure: "I see the alien" vs. "The alien sees me".- We change the sound– such as the intonation: "The alien is friendly, isn't it!" vs. "The alien is friendly, isn't it?"- We change the spelling: "Look – a tea shop" vs. "Look – a tea shoppe".- We change the capitalization: "This is a really big issue" vs. "This is a Really Big issue".- We change the way we expect the discourse to work: "Can you tell me the time? It's three o'clock" vs. the jocular or less cooperative "Can you tell me the time? I can".
Of all these, it is vocabulary which most people immediately associate with the notion of sense. This is partly because of the quantities involved.
In English, for example, we have just a few dozen of sounds to learn, a few hundred sound combination in syllables, and around 3,000 grammatical constructions － but there are hundreds of thousands of units of vocabulary.
So the focus of any semantic approach must lie there, in vocabulary, and that is how it has always been.
But vocabulary within sentence, always.
It is the interaction between words and sentence structure which actually conveys our 'sense of sense'.
Words by themselves do not actually 'make sense'.
Only when they are used within a sentence do they 'make sense'.
Sentences exist to enable us to 'make sense' of words.
That is why sentence study is the foundation of grammar.
Dictionaries, of course, tend to give the opposite impression. Indeed, if we do not know the meaning of a word, we say to ourselves that we will "look it up in a dictionary".
But it is easy to show that most of everyday words, by themselves, convey little sense — or perhaps it should be that they convey too much sense.
It is not possible to work out the sense of a word (e.g. "table", "charge") by seeing the word alone. The ambiguity can be resolved only by putting the word into a sentence: "I am sitting on a table.", "There's a misprint in the table." That is why it is essential for dictionaries to provide several real, clear, sentence-based examples.
Undoubtedly there are many cases where it is possible to ask what the meaning of a word is, and get a sensible answer. This happens when the word has just a single use in a language, as is the case with many scientific or technical terms — "otology", "semiconductor", "phycocyanin". These words are monosemic. Some everyday words are monosemic too — "hand-kerchief", "gaudy", "crybaby". And we are also used to thinking of some proper names in this way, where the word refers to one place, one person, one company, and so on: "Reykjavik", "Lithuania", "Microsoft".
But most everyday words are not like this. They arepolysemic— expressing several meanings. The word "charge" could be something to do with money, crime, soldiering, electricity, or explosives — to take just five possibilities. It does not make much sense to ask "What does "charge" mean?". The only way in which we can find out is by using the word in relation to other words — typically, by putting it into a sentence, so that we can distinguish, for example, "The battery was charged with special chemicals." and "He was charged with homicide."
Isolated words do not lack meaning. Rather, they have the potential for conveying too much meaning. Many everyday words have a dozen or more senses. A common word like "take" may have fifty or more. Plainly, we need to analyze the relationships between words so that we can distinguish these senses clearly. This is what a good dictionary does, and it is what the science of words, lexicology, does too.
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出處/來源：David Crystal, “How Language Works” pp. 190-191, Avery/Penguin, 2007
