One of the best things you can do for yourself when learning a new language is to always have a dictionary ready. Don’t let yourself get stopped in the middle of reading something to go find your paper dictionary or to flip through your bookmarks to find your online one. At least when you’re at home or at the office, keep your dictionary ready at all times. I recommend consistently keeping an online dictionary open.

Find a good online dictionary and use that as your primary source for looking up words. This is the quickest and most effortless way to look up words. Instead of fumbling through your paper one, which can take a long time to find a word, just type or copy-paste the words in. You can probably look up about ten times as many words with an online dictionary as you can in the time it takes to use a paper one.

I always have my Chinese and Japanese online dictionaries open in a Firefox tab, along with all my other resources. I’m not sure if other browsers can do this or not, but Firefox let’s you just open as many browser windows as you want at once. So I open my dictionaries in one window and just keep that minimized until I need to use it. Another nice thing is, you can just shut down your computer and the next time it restarts with Firefox all your saved windows will appear as they were before. This eliminates a lot of extra down time. It might not seem like a big deal, but this kind of time adds up.

There’s another way I use this to help me learn new words. Whenever you look up a word in the online dictionary, find your word and just leave it on that page. Don’t go back to the main search page. This way, when you come back next time you will see that word again. Repetition is one of the keys to learning anything. The more times you see a word, the better chance you will remember it.

Here are the two online dictionaries I use and keep open at all times.
Japanese: http://www.df.lth.se/cgi-bin/j-e/jis/dict
Chinese: http://hmarty.free.fr/hanzi/
They might not have every word in their database, but then you can always go to your paper dictionary for the missing words. I’m not against paper dictionaries. I have about four of them on my desk at all times, but if you want to learn a language quickly then you should learn to manage your time as efficiently as possible.