I would suggest using Anki to drill vocabulary. It's a flash card program that you can get on your computer, iPhone, iPod, etc. The idea behind it is that when you do the flash card you say how well you thought you did (Wrong, Good, Very Good) etc. and based on that the card will not reappear in your deck for a set amount of time. It should appear just often enough for you to remember the word, and the more consistently you believe you're getting the vocab term right, the greater intervals will be in between its appearance. If you get it wrong, however, the intervals restart.
That being introduced, there are a variety of premade decks that you'll be able to find both online and through Anki itself. If I had to suggest a group to start with, I'd look up the 'Japanese Core 2000' deck of cards. It comes in multiple steps (groups of about 100 cards) and you can set how many cards you want to learn per day. The nice thing about it is that in addition to the cards already being made, they have recordings of native speakers saying the words for you, giving you a chance to practice intonation.
I have no idea what your Japanese level is at either, but at some point it might be worth it to try using Japanese -> Japanese Dictionaries when looking up words. At the moment, I use
Yahoo's Japanese Online Dictionary,
Space Alc and
Sanseido's Online Dictionary.
Yahoo is my Japanese -> Japanese dictionary (though it also has a J-E and E-J dictionary), Space ALC I like to use for finding phrases along with words, and Sanseido is good because for a number of words it has an intonation guide (I actually don't remember what each number represents, but if I can find it, I'll let you know. It can tell you whether certain shorter words are High-Low, Low-High and so forth with intonation).
Also not a bad idea, trying to find some native material, reading a few sentences, and picking out some words you don't know. Look up those words, try to find other sentences with them, try to learn their meaning.
Anyways, those are my suggestions. You don't have to do all of them, but they're worth thinking about. If you pick one to start with, I would recommend the Anki deck.