Whether you are translating between languages, or simply trying to understand a foreign language, looking up the meanings of words is a common activity you can end up doing tens, if not hundreds of times a day. Learning to improve your word research process will not only help save time but can also lead to better translations and understanding. I will be writing this most primarily from the point of view of researching Japanese words, but some of the suggestions will apply to any language pair.
It’s important to know what confidence level you need in the result, as that can affect how much time you should spend on researching each word. A word in a straightforward text you are only skimming might take a few seconds, whereas a specialized term in a legal document you are translating as a job might take 15 minutes or longer to get a proper understanding of it. I’ll be giving suggestions more on the detailed side, but you can adjust according to your needs.
First, do an initial search using whatever dictionary is fastest for you. I recommend using a digital dictionary actually installed on your local machine, as both paper dictionaries and websites can add a few seconds (if not more), and that time can add up. You’ll probably instinctively start with the dictionary from Japanese to English (or the foreign language to your native language if you are using a different language pair), which is probably the fastest. But, more often than not, the native language dictionary entries (ex: JP->JP) have more detail, and sometimes better sample sentences, than the native-foreign language dictionaries (ex: JP->ENG). However, if your level in the foreign language in question requires that you usually have to look up more words (resulting in an endless loop of lookups) then you may want to stick to the dictionaries in your native language(s).
Generally, you can glance through the various meanings and pinpoint one meaning which matches the context of the sentence you are dealing with.
However, for some words, even this basic lookup may be problematic. If you can’t cut and paste, then you end up having to use an OCR (generally pretty failure-prone in my experience) or use radicals to lookup Kanji which you can then type in manually for a search. I highly recommend the latter, and you can try using a site like this one to get started.
Another issue you may run into is converting the word into a form that dictionaries can understand. For verbs, this would be the ‘dictionary form’, such as ‘たべる’ instead of a conjugation or derived form like たべます、たべはじめる、たべて, たべろ, or たべたい. Generally I recommend putting in words using hiragana, if possible, since certain ways of writing words (for example 突っこむ vs 突っ込む) may not be in the dictionary. The main exception is words that nearly always written in katakana, for example スマホ, although several dictionaries that I tried have both スマホ and すまほ in them (the latter gives a reference to the former entry).
For i-adjectives the same thing applies, so convert おいしくて or おいしかった to おいしい when you do a lookup. Similarly, change the -sa form to a dictionary-friendly form, for example おいしさ to おいしい。For na-adjectives, you can similarly convert すばらしさ to すばらしい, although sometimes the -sa form is in the dictionary as a separate entry.
For expressions, you have the option to look up the whole thing (ex: 目を通す), or search for one of the parts (目 or 通す) and then see if there is a list of expressions in that dictionary entry. I recommend trying the former first. In rare cases, you may have to use a more common variant of the expression, for example “気を使う” instead of “気も使う”. Also remove adverbs or other words that add emphasis or ornamentation, for example search for ”頭が上がらない” instead of ”頭が全く上がらない”.
Even more so than with single words, with expressions you can run into problems with different combinations of kanji/hiragana/katakana (ex: 目をとおす doesn’t have a hit in some dictionaries), so if you get stuck try with hiragana only (めをとおす). As with single words, you should convert verbs in expressions to dictionary form (目を通して probably won’t have a hit but 目を通す will). However, sometimes te-forms of verbs that are commonly used as adverbs with other verbs (like 通じて or 関して) will have an entry of their own.
Also, if there are particles before or after words, generally you should remove them (except for expressions which have a particle in the middle). This even applies to words which are almost always used with a certain particle, for example に関する is not in the dictionary but 関する is. Another place you can get stuck is when there is an extra small tsu (っ）added in certain words, as can occur in casual conversations or other informal media like blogs. For example すっごい generally won’t be in dictionaries, however とっても generally is (which I think has been around much longer). Also, remove these characters from the end of words before lookup (ex: use はやい instead of はやいっ)
Once you’ve done your first lookup (which is hopefully fast via a local dictionary), then you may decide you want a second opinion and do a similar search using an online dictionary. There are many out there, but I use Dictionary Goo pretty consistently and think it generally has good coverage and examples.
As you have probably noticed, example sentences in many dictionaries have translations with out-of-date or infrequently used terms. But keep in mind the most important thing is understanding the word yourself (even if you are doing translations). Don’t expect the dictionary to give a completely natural translation of the word. Sometimes you may not be too familiar with the English word(s) used to describe a Japanese word or phrase, and doesn’t hurt to look those up. While thesauruses can be a great tool to craft natural sentences during translation, I find them useful even when just trying to understand the English explanation of a Japanese word. Just be careful that synonyms of a word often have different shades of meaning that may not be present in the original word you are researching. You can also use thesauruses in the source language for more information. Here is a good Japanese thesaurus that typically has good lists of synonyms.
Another option that you can try is doing a Google search. I generally don’t recommend this until you’ve tried one or two dictionaries as web searches will generally be more time consuming and require more parsing of the results. If you just put in the word by itself into Google (ex: パソコン), often you’ll get sites selling products related to that keyword and not necessarily the definition you are seeking. For some words (ex: 顔) you can get a Wikipedia page hit, which can be very informative, but (if in Japanese) this can require a lot of challenging reading. Either way, if you have the time you can read through some random pages about the word(s) in question to build up some related knowledge that is hard to get from a dictionary entry.
The simplest way to look up English parallels to a Japanese word or phrase is simply adding “英語” to the search. For example “パソコン 英語” will give some useful results. You can also add とは instead (ex: パソコンとは) which will tell Google you want a definition, which is an easy way to get a definition in Japanese. (Note: in all examples where I give terms in double quotes like in this paragraph, please do not use quotes in the search unless I say otherwise).
It’s not uncommon to see a word used in a way that is ‘stretched’ from the formal meanings in dictionaries. Fortunately, just from the context you can sometimes guess what the word means. For example, the common word ごちそうさま can be used sarcastically when someone is bragging about a personal story. But if you wanted to find evidence of this, you could do a google search for “ごちそうさま brag” and you’ll find a useful article in Japanese about this usage. (This use is briefly described in one dictionary I checked, but the online article is much more detailed and informative)
Similarly, if you want to a quick check whether your gut feeling about a word is correct you can search for something like: “めまい dizzy”. This also can help you decide whether this is an appropriate translation, since you may find examples where others have translated the term in question in the same way.
One of the advantages of advanced search sites like Google is that some of the tweaking you have to do with dictionaries becomes unnecessary. For example if I search for 突っこむ it will say “Did you mean 突っ込む?”
When searching for words online, besides using Japanese kana (日本語・にほんご・ニホンゴ) you have the option to use romaji (ex: “nihongo”). Generally, dictionaries that use romaji (example) are simpler and have less detail because they are targeting basic students. For that reason, I rarely use them myself. However, if you are still new to Japanese it isn’t a bad idea, you might even find them easier to use than a more advanced dictionary. But I usually wouldn’t recommend using these for translation, especially if it is a paying job.
Another trick you can do is if you find a sentence with two or more words you want to look up, you can copy that entire sentence and paste it into Google’s search window, then just cut out the unneeded text around one of the words you want to search, and execute that search. Then re-paste the whole copied portion and cut off the text around another word or phrase. Depending on what app you are viewing the source text in, this can sometimes be slightly faster since you don’t have to switch between apps.
Another thing you keep in mind is the reliability (or trustworthiness) of the data you are dealing with. Common dictionary sites (like Dictionary Goo) and dictionary apps (like Mac OS X dictionary app) generally can be considered more reliable than random blogs or other websites online. If you need a more definitive answer, consider checking with a native or a forum like Japanese Language Stack Exchange. When using internet forums, however, be sure to note the points/experience of those that answered your post. If it is someone new to the forum their response may be less reliable, and you shouldn’t expect others will necessarily point out mistakes in post responses.
If you are dealing with really uncommon words or special domain words, you may need to refer to a domain-specific paper or digital dictionaries. Here is one with business terms as an example, though I haven’t used it myself. Generally, I haven’t needed these.
Another option is using custom translation dictionaries, but so far I have not found much need for these. I imagine if I was doing translation full time (or doing more non-fiction) these would be more useful. But even for longer fiction works, it is a good idea to search through all the text you have translated so far for a specific work to see if/how you have translated a specific word. I would generally err on the side of consistency–essentially using the same term as you did earlier in the same work–unless it’s used in a different situation or you want to avoid repetition.
As a final note, I have heard of several people who use Google Translate as their first step when doing translations (although none of these were professional translators). Last time I checked, Google Translate still was horrible for automatic translation of Japanese to English text. Because you will only get single word suggestions for each term, and because of the translations will often be a train wreck for more complex sentences, I think this is mostly a waste of time. I would only suggest this for people who have no Japanese knowledge, or want a *really* rough understanding of non-fiction passages. For a majority of fiction, I feel that the ‘atmosphere’ and ‘tone’ can be as important as the content itself, and automated translation hasn’t even begun to understand these things.