I know people spend years learning to do just this, and I know there is no such thing as a get-fluent-quick scheme that actually works. But I am going to introduce you to a power tool that, if you have a workable level of Japanese (upper beginner/lower intermediate) will make your Japanese writing far more correct and natural.
I am talking about Sentences. You probably already know that Denshi Jisho has a sentences section and you may be using it. But lot of people don’t realize how powerful this tool actually is or how to use it to best effect. There is also a much bigger database of sentences at Space Alc. I use both of them all the time (Edit: since this was written the new beta Denshi Jisho has a sentences function linked to Tatoeba that produces more results than the old one).
Suppose you are writing a story or a post in Japanese. You have some idea of how to say what you want. But is that really how a Japanese speaker would put it? Or are you writing Eihongo (the counterpart of Japlish).
Can those words actually be used in that way in Japanese? What one should do now is try to find a precedent for the way you are saying it.
So if you think you know how to express what you want but aren’t sure that it is natural or correct Japanese, enter the key phrase into the sentence search box of one or more of the engines recommended above (or use a regular search engine if your Japanese is good enough) and see how it is actually used.
Cut it down to the basic turn of phrase you are worried about (these are databases of human-made sentences, not translation engines [thankfully], so you won’t find your exact sentence). See if that combination of words is in fact used with that meaning and nuance.
You can do this with very limited units such as てばかり – essentially asking “show me the way ばかり is used with a verb in て-form”. As you see, you can use this for elucidation of grammar points in a more general way, but what we are doing here is trying to find out if the way we are using it in our particular sentence is going to be natural, correct Japanese.
We can also expand it a little. If the word we are coupling with ばかり is very common, we can try putting in that exact combination and see whether it is used and how.
Of course if the phrase is not in the database it does not mean that it isn’t usable (though if you are using Google raw, it probably does), but it is a large database, so if the phrase is a common collocation, it is likely to be there. If it isn’t there it may be worth considering re-phrasing with something you can be more confident about.
You can also work the other way and put in the general idea you want to convey in English and see what Japanese examples you get. Expect to sift through various non-relevant examples. Be prepared to expand and contract your input (whether in English or Japanese) since if it is too long and explicit you may not find it and if it is too short it may not be explicit enough.
Remember also, when faced with pages of examples, most of which are not relevant, that a good way to sift through them is to use your search-engine’s on-page search function. Search in the language you didn’t input into the database in order to narrow down the results to your target meaning. For example, if you are wondering whether – and how – you can use 代わりに in the sense of “substitute”, you can search 代わりに which on Space Alc gives you six pages of results. You can then enter “substitute” in your browser’s page-search to look for examples of the usage you want.
Language works a lot by collocations – words that are continually found together. You make a fuss, but you throw a tantrum and you get into a bad mood. The phrase-elements are not interchangeable. Much as (Western) people may want to think that their own speech takes the form of personally unique combinations of words, in fact it is built up of countless collocations, or word-groupings that belong together and sound odd and “foreign” if different groupings are used.
Japanese is the same so what you are doing here is searching not only for correct grammar but natural collocations – the words that actually habitually go together in the language, and not only broadly mean what we are trying to say but convey the correct tone and nuance.
I confess I am a little “obsessive” (to use the pathology-based argot of current English) about looking up collocations and phrases. If I don’t remember a turn of speech from somewhere I try to find a sentence-example. If I can’t do that I usually consider re-phrasing.
This is not really “obsessive”, however. It is how you use English. In English you are continually guided by precedent. You know which words go together and which don’t.
Even sub-standard, ill-educated English goes by precedent. Very few native speakers over the age of six actually make their own grammatical mistakes. They use the bad grammar of their group. Large numbers of English speakers say “it don’t make no difference” but only infants and foreigners say “it not make difference”, or indeed any other variation on the phrase. Real, natural language is ruled by precedent at every turn.
Japanese speakers, of course, generally believe in precedent and conformity in speech. English speakers are prone to believe they hate conformity, but they are in fact just as precedent-bound as any other linguistic group.
So what I am saying is that you want a precedent for what you say. It is how natural speakers speak. Native speakers have an internal bank of precedents. We are using an artificial bank to simulate the same process and use correct, natural Japanese.
Fortunately, using this helps us to build our own internal bank too. The effort of researching the right way to say a thing helps it to stick (put it in your Anki too if it seems appropriate)
One caveat though. As far as possible, try to construct the phrase first. Putting what you want into the database in English can be useful but should be your last resort. As far as possible use words you already know even if it means simplifying your meaning a little. If you have to search in English, try to select from the results a Japanese phrase that you understand well. Don’t dump a chunk of blind-faith grammar into your writing.
There are a lot of reasons for this. Your writing should stay yours. It should be constructed of elements you understand and have control over. Otherwise you may be building a Frankenstein out of half-understood parts.
That being said, the use of sentence-searching to enhance your writing will help you to use natural, correct Japanese better than any other single tool. Precedent is how language is built up in the child mind. Using it is the most organic way of expanding your use of language.
Of course you will be using native materials to build a true bank of precedent. More and more you will know how to say something because you recall this character in that anime saying something along the same lines. Online sentence-databases are a substitute for the one we will eventually, like all fluent speakers, be carrying in our hearts (I don’t say “heads” because I believe our hearts is where we truly carry them).
Just use the database method in as pure and organic a way as possible, and you will be writing natural and organic Japanese to a far greater extent than would otherwise be remotely possible.